Yes, most airplane cargo holds are pressurized. This means that the air pressure in the cargo hold is the same as the air pressure in the passenger cabin. This is important for two reasons:

To prevent cargo from expanding or contracting. As the aircraft climbs, the air pressure outside the aircraft decreases. If the cargo hold was not pressurized, the air pressure inside the cargo hold would also decrease, which would cause the cargo to expand. This could damage the cargo or even cause the aircraft to crash.

To allow people to work in the cargo hold. If the cargo hold was not pressurized, the air pressure inside the cargo hold would be much lower than the air pressure outside the aircraft. This would make it difficult for people to breathe and could even cause them to pass out.

Not all cargo holds are pressurized. Some small cargo planes, such as those used for delivering urgent medical supplies, do not have pressurized cargo holds. This is because the cost of pressurizing the cargo hold would be too high for these small planes.

Cargo planes are loaded in a variety of ways, depending on the type of cargo being carried. For example, live animals are typically loaded into the cargo hold in special containers that are ventilated and heated or cooled. Perishable goods, such as fresh fruits and vegetables, are also loaded into special containers that are kept at a cool temperature.

Other types of cargo, such as furniture and machinery, are typically loaded by hand. This is done using a variety of tools and equipment, such as forklifts, pallet jacks, and conveyor belts. The loading of cargo planes is a complex process that requires careful planning and coordination. The goal is to load the cargo efficiently and safely, while also ensuring that the cargo is secure and will not shift during the flight.

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There are no restriction for carrying non-hazmat cargo on passenger flights. In Alaska, it is a common practice for Alaska Airlines to carry both passengers and cargo on the same flight to and from many rural communities. They use a temporary (cosmetic) bulkhead to separate the two compartments.

In Alaska, they will outfit the B737 with about 7–10 rows at the front of the aircraft for passengers, install a temporary cosmetic bulkhead, and then load cargo in the remaining rear of the airplane.

In 1993, I was on a flight outfitted like this for a flight from Dillingham to Anchorage Alaska. As the aircraft descended on final approach we could hear a bang-Bang-BANG-BOOOM!… travel from the tail to the front and hit the bulkhead behind the seats. Apparently a cargo tie-down strap or some other heavy metal object had not been secured and when it hit the bulkhead near several women, they screamed!!! So. I guess the bulkhead isn’t just cosmetic :)

If the plane is pressurised, the cargo area almost always is as well.

Unless it’s a military transport, which often have a flight deck and small passenger area with separate pressurisation system from the cargo hold, which allows opening doors at altitude and potentially flying with the hold unpressurised.

There may be a few exceptions. I’m aware, for example, of some light twins that have small baggage compartments in the engine housings that are not pressurised, though the cabin is.

Certainly civilian jet airliners with pressurisation the hold is pressurised; the reason for that is that it is much easier to make a tubular pressure vessel, and if you pressurise the hold you don’t have to make the floor a pressure bulkhead, so the plane can be lighter and simpler.

yes passengers can fly in the pressurized baggage pit. those people pay large fees. and they are DEAD. dead people ride in cargo pits on aircraft lots of the time.

live people do NOT fly in cargo pits. the temperature is not controled. the cargo pits are pressured but not heated like the cabin. so the temperatures in cargo pits can be very cold. some aircraft have heated cargo pits but recycle rate is not as high as in the passenger compartment. so it is not comfortable for humans.

For purely engineering reasons.

It would involve the construction of an extremely strong passenger floor to take the differential pressure between the pressurized cabin and the cargo compartment, which presumably is exposed to the outside pressure.

It would also involve the redesign of the entire fuselage to take pressure loads in the upper (passenger) half and no differentials in the lower half.

This would make commercial flight prohibitively expensive.

A pressurized cargo is much cheaper to design. In case of necessity, it is even ventilated and temperature controlled (when, for example, carrying live animals).

And, in case of a cargo fire, a system of valves stops the ventilation into the cargo compartment. The use of remotely operated fire extinguishers and the lack of further oxygen coming in is considered enough to smother the fire.

Things have gone wrong, of course, and lessons learned.

https://www.ntsb.gov/investigations/AccidentReports/Pages/AAR9706.aspx

20 years ago today: ValuJet Flight 592 crashes in Everglades, killing all 110 aboard

FedEx Express Flight 1406 - Wikipedia

Short answer: yes MOST do. A great deal of cargo that is shipped requires temperature and pressure control. Temperature of the cargo is controlled via the pressurization system. Some live cargo that comes to mind: Tropical fish, bees, horses, breeding animals, pets, computer equipment, packaged food, biomedical supplies, and much more.

Here is an experiment that everyone can do on any airplane: Buy a bag of chips (crisps). Do not open it. Take it on your flight with you. Observe how it expands as you climb and reach your cruise altitude. At cruise it will look like an over-inflated mylar balloon. Now, if you were on a jet at 37,000 feet, for example, you could picture that without pressurization that bag of crisps would have about 4 x as much pressure in it. It would explode. Likewise, much cargo is in wrapping, packaging, containers, bottles, etc. Without pressurization control it would be damaged.

Now, I said MOST because freight is also shipped to smaller stations via smaller planes that do not fly above 10,000 feet. This is a Cessna 208 caravan. It is not pressurized. the aircraft in the back are pressurized. Therefore, if you are shipping something to an area with only a rural airport your best bet is to collect it at the major hub and then ship it via surface to the final destination.

Long answer:

Commercial airplanes, both freight and passenger, do not fly above 10,000 feet without pressurization. For commercial jet and turbo prop aircraft, pressurization provides : passenger comfort, temperature control, and structural support.

For aircraft that do fly over 10,000 feet above sea level:

Regarding structural support: think of the aluminum or composite fuselage of the aircraft as a balloon. By pressurizing it the fuselage gains rigidity and strength. This is why aircraft are designed to takeoff and land at an internal pressurization that is greater than outside air pressure. (For reference, the inside air pressure is equal to that of an altitude that is 200 feet lower than the airport upon departure or arrival.)

Above 10,000 feet, humans and animals that are not acclimatized will become hypoxic. That is they will not receive enough oxygen from breathing the ambient air. There are tables, for example, of “TUC” which is Time of Useful Consciousness at various altitudes. At 41,000 feet without pressurization one would have about 15 seconds TUC before blacking out and eventually dying. You can see the air pressure and oxygen here: Altitude air pressure calculator. And here is a table of TUC: Oxygen Requirements, Time Of Useful Consciousness, and Intercept Procedures.

Also, one will freeze to death rather quickly at that altitude, as ambient temperature is around -50 degrees C. All of the liquids in the cargo will freeze as well. Temperature sensitive cargo — computer hard disk drives come to mind — may be damaged by both the pressurization change and the frigid temperature.

It is important to note that some aircraft, the Boeing 737, for example, have class D cargo holds that provide pressure and some temperature control, but do not recirculate air, and therefore cannot carry live cargo for more than about 3 hours. These cargo holds were designed to prevent the spread of fire from the cargo hold if there is a fire in the baggage. The Valujet 592 crash precipitated this. https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9706.pdf

So if you are planning to send live cargo such as dogs, bees, chickens, etc., it is very important to declare it as such. This is why some airlines do not accept pets for transport in the Cargo Bin. Southwest is an example. They fly only Boeing 737s, and on the 737 the air is pressurized, but does not circulate in the cargo hold. If you did somehow check your pooch into the cargo hold with the luggage on an SWA flight on a flight from Oakland to Midway, you would need a taxidermist on arrival.

If you are referring to commercial passenger jets, the answer is yes.

The fuselage is designed to withstand the stresses of internal air pressure based on “hoop Stress”. That is, the pressure rating is based on the structure being circular or in some cases oval. The floor of the passenger area is flat and not designed to withstand a difference of air pressure between the passenger area and the cargo hold.

There have been incidents where there was a sudden pressure loss in the cargo hold (at altitude), causing the collapse of the passenger floor.

The DC-10 exhibited this several times do to a faulty design of the latching mechanism on a cargo door. The door blew out, the resulting instant loss of pressure in the lower compartment caused the remaining pressure in the upper compartment to collapse the floor. In at least one instance, several seat assemblies were lost (including passengers still belted into their seats). They were actually tracked on radar as they fell to earth. As I recall, this particular incident happened in Turkey.

I fly passenger Airbus A330s and A340s. I've never flown a cargo only aircraft so I can only answer about the passenger Airbus.

We can set the temperature in the back cargo compartment (the "hold" or the "bulk" we call it) between 5 degrees Celsius and 25 degrees Celsius. The normal position for the selector is around 15 degrees Celsius. If we are notified that we carry a pet, which would normally be loaded in that hold, we will normally set the selector around 20 to 22 degrees Celsius.

This is from our operating manual of the airplane:

Minimum selector setting: 5 °C (41 °F)
Maximum selector setting: 25 °C (79 °F)
Middle position: 15 °C (60 °F)

Cargo compartment temperature may vary due to such factors as flight duration, outside temperature, and cabin temperature. As a result, the actual temperature may be higher than the one indicated by the selector position.

The hold is actually together with the aft cargo compartment one big open space.

The forward cargo temperature is normally not set because the selector for that is optional and most airplanes don't have it with the airline I fly, which is why we put pets in the hold.

Different types may have different settings.

Edit to elaborate on the comments:

• There's no need to worry about checked in luggage items getting frozen. The temperature in the cargo hold would under normal circumstances be around 15 degrees Celsius. That's chilly, but not freezing. I'm not sure how the physics and chemistry inside a perfume bottle work but my guess is that's it won't have an effect on the quality of the perfume or alcohol you transport. When we have live cargo, we turn up the heat a notch so the animals are comfortable and it's closer to room temperature. Of course, items have to be transported to and from the cargo hold on the airplane and then it may be that they are exposed to the weather conditions at the airports they transfer through, sometimes for a significant amount of time: snow, rain, sun, cold, heat...
• What we call the "hold" or the "bulk" is actually on the Airbus 330 and 340 the aft cargo section. There's a separate smaller access door to it from the outside. It's not a separate space inside the airplane as there's only a net that keeps this zone isolated from the zone just in front of it. It distinguishes itself from the rest of the cargo area in that there are no special cargo containers needed to load the items in first. Please notice that I'm only talking about a passenger A330/340/320 now as I have too little experience with other types. I have a little 737-200 experience and there were no cargo containers needed at all, cargo could just be piled up inside the plane.

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(Note the small "bulk cargo compartment door" aft of the aft cargo compartment door. This allows separate access to the "bulk" or "hold" for items like baby strollers or animals that aren't conveniently loaded in cargo containers before being put on board.)

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(The bulk cargo compartment forms one big space together with the aft cargo compartment so in theory whatever the temperature in the aft cargo compartment is, is also the temperature in the bulk cargo compartment)

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(Here's a view from inside the aft cargo compartment towards the back of the airplane. The open door is the aft cargo door. Note how only a net separates the "bulk" or the "hold" from this aft cargo compartment.)

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(Here, similar to the A320/330/340 you can see all the cargo doors opened: forward, aft and the smaller bulk cargo doors)

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(The small hatch to access the bulk is convenient for last minute items or pets because they don't need to be put in cargo containers in order to be loaded on the plane, but just a net over them to keep them in place.)

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(Other items, like checked in luggage or cargo, go into a cargo container like depicted here before being loaded onto the airplane. This prevents items from shifting significantly and keeps the airplane stable and balanced. Items that go into the bulk are not loaded in one of those containers but just kept in place with a net.)

Some are:

Some are not:

Basically all of the large, airliner-derived ones are (like the 777F in the first picture), some of the smaller feeder aircraft are not (the Cessna 208 Caravan in the second picture).

• The forward cargo hold temperature was 5 degrees Celsius.
• The bulk cargo hold was at 14 degrees Celsius.

The temperature can be regulated depending on the cargo you are carrying.

We carry a lot of sensitive items in the cargo holds. Cosmetics, medicines, animals/pets, human remains and other things that need a humane environment to come out in one piece. If the cargo is not pressurised, every time you open your checked baggage after a flight, there would be a big mess with your shampoos and lotions spilled all over your clothes. If you had a pet in there, it would have died. So, yes the cargo holds need to be fully pressurised to make sure we are able to transport the goods safely and in a good condition.

Pressurised airplanes have two pressure bulkheads. An aft pressure bulkhead and a fwd pressure bulk head. The aft bulkheld seals the aircraft from the tail cone and the fwd bulkhead seals from the aircraft radome. Thus, the fuselage area in between these two bulkheads are completely pressurised. This includes all of the passenger cabin area, the cockpit and all of the cargo holds in the aircraft.

Aft pressure bulkhead of a B747.

No. All transportation operations do everything possible to maximize revenue, which means getting cargo both ways.

Nearly every transportation route has a heavy direction and a light direction. A balanced trade is ideal, but seldom happens in the real world.

Such cargo as there is in the lighter direction is universally referred to in the transport business as “backhaul” cargo. Backhaul cargo is whatever is available to generate some revenue for the equipment as it repositions BACK to the place where the greater quantity of cargo is generated, as it must, to pick up the next load of high-paying base cargo, the freight that accounts for the majority of the revenue.

For example, since China has become a manufacturing powerhouse, essentially all routes to/from China have more manufactured goods cargos outbound from China than into China. Asia-US, for example, has more airfreight moving eastbound (Asia to US) than westbound (US to Asia); same thing in the container shipping on that route.

So the planes (and ships) are loaded with whatever cargo can be found to generate some revenue for the backhaul, the point being that some revenue, no matter how little, is better than no revenue at all. Rates in the backhaul direction will simply drop to whatever level maximizes the revenue that can be generated. Even if the planes were to achieve full loads, it would be with cargo that does not pay well, so it is still backhaul in the sense that it is moving only at super low rates just to fill up the empty space. It is the cargo moving in the heavy direction that generates most of the revenue and justifies the service; the backhaul a just a little icing on the cake, but short of some odd compelling and unavoidable reason, no transportation company willingly returns its equipment empty.

Yes. To depressurise the ex-cabin, now cargo area, would require inserting a pressure bulkhead behind the flight deck, which would be extremely expensive and difficult. The plane is already equipped for pressurisation. Why go to the expense and complexity of depressurising a pressurised hull.

Secondly, a lot of freight may not like being depressurised. Gizmos in sealed plastic containers (the ones that are so difficult to open) would ballon out. Bubble wrap would expand in inconvenient ways. Even before converting the aircraft, a lot of freight travels, pressurised, under the floor. Shippers do not anticipate their goods being depressurised.

Most freighters are pressurized, but not all. Most civilian fighters are derived from civilian airliners, and those are all pressurized. Some specialty aircraft, the Airbus Beluga, the Boeing Dreamlifter, are not.

Many smaller aircraft are not pressurized, and are used to haul freight. FedEx has a couple of hundred Cessna 208 Caravans, which they use on short haul, low density, routes, none of those are pressurized:

There are dedicated cargo airlines like FedEx, DHL etc that specialize in just flying cargo around the world and have extensive networks.

The airline I worked for (Qantas) besides being a passenger airline also operated numerous cargo aircraft as well. Besides flying some cargo in the holds of passenger flights They operate dedicated cargo flights on B747, B767, B737 and BAE146 around the world. Domestically in Australia the cargo flights used to operate overnight. Here’s some pictures of one of the converted B737 freight aircraft…..

Cargo was carried on containers on the main deck as well as the cargo compartments. The overnight freighters would carry mail , parcels and whatever had to be there. It could be perishable goods like fish and frozen food or just your drunken eBay purchases. The aircraft carried everything.

All apart from An12, IL76 and An124.

An12 has no option to pressurize the cargo hold at all. The other two have the possibility to close off completely the cockpit and crew compartment and the cargo hold to be depressurized. It saves fuel but many types of cargo require pressurization for transport.

Other factors have to be considered as well - we had a 40-foot container literally imploding on landing. New container with still airtight seals on an An124 leaked out internal air during the pretty long flight and on landing the increasing pressure pushed the walls in as the outside pressure was rising much faster than the air could be squeezed in through the seals to compensate..

Yes. As a matter of fact, I have flown such flights as a pilot with tons of cargo in the cabin. The aircraft manufacturer has a certain set of procedures to set up the cabin to carry the cargo. The seats are usually laid with covers and then the boxes are placed over the covers so that the seats are not damaged in the process. Once the cargo is in place, they are secured using aviation grade straps which keeps them in place.

Cargo placed in the cabin. In this picture, they are not secured yet. But you can see the covers and straps which will used to hold boxes in place.

You can carry quite a load of cargo even in an aircraft the size of A320. About two weeks back, we carried close to 15 tonnes of medicine in the cabin and cargo holds of an A320 in a COVID 19 relief flight. Some of those medicines were quite sensitive to temperature changes and how they get placed for transport. Those boxes were specifically carried in the cabin.

Yes, cargo planes generally fly at similar speeds to passenger planes. The speed of an aircraft is primarily determined by factors like its design, engine power, and aerodynamics rather than whether it's carrying passengers or cargo. So, whether it's transporting people or goods, a plane's speed remains relatively consistent.

And when it comes to the fastest cargo planes, one notable example is the Antonov An-124 Ruslan. This massive aircraft is capable of reaching speeds of up to 550 miles per hour (885 kilometers per hour) while carrying heavy cargo loads. Another example is the Boeing 747-8F, which is also known for its impressive speed and cargo capacity.

Antonov An-124 Ruslan.

Boeing 747-8F

These aircraft, among others, are designed to efficiently transport goods across long distances at high speeds, ensuring timely deliveries around the world.

However, there might be some variations based on specific models or flight conditions, but in general, cargo planes do not fly noticeably faster than passenger planes.

The answer is yes and no depending on the class of cargo hold you are flying on top of. This handy chart shows you what is what. Class D is no longer used and class E is for dedicated cargo planes.

Basically with most classes they look to the flame proofing air tight liner to prevent flame and smoke getting into the cabin.

There are at least four kinds of cargo operations:

1. Scheduled round trip operations. They operate like scheduled passenger flights.
2. “Package carriers” - like FedEX that collects packages from certain city, flies them to their hub (like Memphis in USA) and then distribute those packages with other flights from the hub to the final destination. These are also scheduled operations.
3. Some operators fly “on demand cargo flights”, where aircraft will wait for new cargo at the airport were it had landed with the previous load. They may make “repositioning flights” (that are empty), but they do not “return empty to home”.
4. Then there is Volga-Dnepr airlines that operate 12 An-124 aircraft. It is the biggest cargo airliner (that has been mass produced - total of 50 something were built).
   They are specialized in overweight and oversized cargo. Google “Volga Dnepr airlines”. That “one of a kind business idea”!
   (Once they had first to build an airport with some 10 000 foot runway to complete the mission!)

Cargo planes generally carry commodities shipped by air and thus have high values per unit or are very time-sensitive, such as documents, pharmaceuticals, fashion garments, electronic goods, perishable items, production samples and seafood products shippers should choose packing materials carefully when preparing for a cargo flight. They most commonly use cardboard boxes. Air cargo system is vulnerable to several security threats including to plots place explosives, illegal shipments and hazardous materials. Some of the biggest air cargo chains are FedEx, Qatar airways cargo, UPS airline, Emirates Skycargo, Cargolux etc. Types of aircraft used are B757, B737, A330, A340 and one of the biggest cargo aircraft B747-F

Cargo airline work haul

From pickup to conveyance, the cycle is straighforward. Your supplier will organize with a nearby transporter to get up at your distribution center or holding office. When the payload is stacked, the transporter will delicate the shipment to the air terminal, where it will be put onto a plane. At the point when shipment shows up at the arrival destinations airport the transporter will orchestrate pickup and conveyance

Yes, turbulence is uncomfortable for everyone, including the flight crew.

That being said, most flight crew will have considerably higher tolerance for turbulence than most passengers, and crews flying freighters are considerably more likely to just ignore some light turbulence than crews flying passengers (the boxes* neither shriek, nor write nasty letters to the airline).

But once the turbulence gets to moderate - pretty much everyone will try to avoid it if they can.

*Cargo flights carrying animals, especially large ones, often studiously avoid turbulence - a horse that’s been thoroughly spooked is a straight up danger, and may well end up needing to get put down, even if they don’t hurt themselves.