A few US cargo airlines use new or recently built aircraft to carry their freight, but most use older airplanes that normally wouldn't be certified to fly passengers anymore, like the Boeing 707, Douglas DC-8, Ilyushin 76. Examples of the 60-year-old Douglas DC-3 are still flying around the world carrying cargo. Short range turboprop airliners such as the Fokker Friendship and British Aerospace ATP are now being modified to accept standard air freight pallets to extend their working lives. This normally involves the replacement of glazed windows with opaque panels, the strengthening of the cabin floor and insertion of a broad top-hinged door in one side of the fuselage.
A number of cargo airlines carry a few passengers from time to time on their flights, and UPS once unsuccessfully tried a passenger charter airline division.
These cargo airlines, amongst many others, have importance in the history of air cargo: