Cargo Planes

Belly cargo is freight carried in the lower hold of a passenger aircraft, beneath the cabin, alongside checked baggage. Airlines sell this space on their scheduled passenger routes, so it reaches many more airports than dedicated freighters do. The trade-off is size. Freight has to fit through the lower-deck hatches and within the hold's height, which rules out tall crates and large machinery. Belly space also depends on how much baggage the flight carries and on the passenger schedule. It suits boxes, small pallets, documents and parts that can share a flight. For anything taller, heavier or tied to a hard deadline that no passenger flight meets, a freighter or a dedicated charter is the usual answer.

A passenger-to-freighter conversion, often shortened to P2F, turns a retired passenger jet into a cargo plane. The seats, galleys and overhead bins come out. A reinforced main deck floor with rollers goes in, along with a large cargo door cut into the side of the fuselage and a rigid barrier behind the cockpit. Windows are usually plugged. Converted freighters extend the working life of an airframe and add cargo capacity faster than new aircraft can be built. Common conversions include the Boeing 737, 767 and 777 families. Once converted, the aircraft loads pallets and containers on the main deck much like a factory-built freighter, although door size and floor strength can differ from the original freighter version.

A combi aircraft carries passengers and cargo on the same main deck. A movable partition separates the cabin, usually at the front, from a cargo section at the back that loads through a large side door. The lower hold carries baggage and more freight. Combis let an airline serve routes where neither passenger demand nor cargo demand alone fills an aircraft, which made them common on remote and island routes. Few combis remain in service today, because dedicated freighters and passenger aircraft with large holds have taken over most of that work. A related term, preighter, describes a passenger aircraft flown with cargo only, sometimes with freight strapped onto the seats or the cabin floor.

It depends on the aircraft, and the range is wide. A Piper PA-31 carries about 1,200 pounds (about 540 kg), and a Pilatus PC-12 about 2,400 pounds. Narrowbody freighters such as the Boeing 737-400F carry about 45,000 pounds. Widebodies go much further: a Boeing 767-200F carries about 92,500 pounds, a Boeing 777-200F about 222,000 pounds and a Boeing 747-400F about 274,000 pounds (about 124,000 kg). Volume matters as much as weight. The Antonov An-124 offers about 36,000 cubic feet of space, the most of any aircraft commonly chartered for freight. Every figure is a maximum, and the real load on a given flight also depends on fuel, distance and the airports at each end.

The C-5M Super Galaxy is the largest cargo plane in the US Air Force. According to the Air Force fact sheet, it has a maximum allowable payload of 281,001 pounds (127,460 kg). It loads through a nose that lifts upward and a rear ramp, so vehicles and outsize equipment can roll on at one end and off at the other. The C-5M flies strategic airlift, moving heavy equipment and supplies over long distances between major bases. Its size means it needs long, strong runways. The C-17 Globemaster III, the next largest, trades some payload for the ability to land on short and unprepared airfields. Neither aircraft is available for commercial freight.

The C-17 Globemaster III is much bigger. Air Force figures put its maximum payload at 170,900 pounds, carried on 18 pallet positions. The C-130J carries about 42,000 pounds, so the C-17 lifts roughly four times as much. Both aircraft are military airlifters with high wings and rear loading ramps, and both can operate from short and rough airfields. The C-17 is a four-engine jet built for strategic and tactical airlift over long distances. The C-130 is a four-engine turboprop, designed for shorter tactical missions into small and austere strips. A stretched version, the C-130J-30, adds cargo space. Both serve military missions and are not chartered for commercial freight.

No, but many cargo flights do run overnight. Express networks collect parcels in the late afternoon and evening, fly them to central hubs overnight for sorting, then fly them out again before dawn for morning delivery. Night flying also uses quieter airspace and airport slots that passenger schedules leave open. Plenty of cargo flies in daylight as well, in the bellies of passenger jets and on scheduled freighters. Charter flights keep no fixed schedule at all. A dedicated cargo charter departs when the freight is loaded, whether that is at noon or at three in the morning. Cargo pilots therefore work a mix of day and night duty, depending on the operator and the routes it flies.

Three things limit every load: weight, volume and the door. Each aircraft has a maximum payload, and dense freight such as steel parts or engines reaches that limit first. Bulky but light freight, such as panels or foam, fills the cargo space before it gets heavy. The door sets a hard limit on single pieces. On a Boeing 747-400F, the nose door measures 140 by 98 inches, while the Antonov An-124's cargo opening is 251 by 173 inches, which is why it carries the largest pieces. Floor strength, the length of the hold and the runways at each end narrow the options further. A shipment's largest piece and total weight together decide which aircraft can carry it.

ACMI stands for aircraft, crew, maintenance and insurance. In an ACMI lease, often called a wet lease, one operator supplies the aircraft with its crew, maintenance and insurance, and the customer pays by the block hour while covering fuel, airport fees and handling. Airlines use ACMI to add freighter capacity quickly without buying aircraft. A dry lease supplies only the aircraft. The customer provides its own crew, maintenance and insurance and flies the aircraft under its own operating certificate, usually for months or years. Both terms come up when companies buy or lease cargo planes. A shipper who simply needs freight moved does neither, because a charter books the whole flight with the aircraft, crew and operation included.

Some can. Small turboprops such as the Pilatus PC-12 operate from short, unpaved, gravel and grass strips, which makes them useful for remote job sites and small towns without a major airport. Among jets, the DC-9 15F can use shorter runways than most, which opens up smaller regional airports. Military airlifters such as the C-17 and C-130 are designed for short and austere airfields. Large widebody freighters, including the Boeing 747-400F and 777-200F, need long, strong paved runways and airports equipped to handle them. When a destination has only a short runway, the aircraft choice narrows quickly, so the nearest suitable airport and the truck leg from it become part of planning the flight.