The Lockheed C-5 Galaxy and the Boeing 747 were both pioneers in the widebody aircraft category, with the C-5 making its first flight in June 1968 and the 747 entering service in January 1970. While their primary roles differ—the C-5 as a military cargo transporter and the 747 as a commercial airliner—both share several design similarities, including a second deck for the cockpit and use of high-bypass turbofan engines.
The United States Air Force (USAF) initiated development of the C-5 Galaxy through a Request for Proposal in 1964 for an aircraft much larger than its predecessor, the Lockheed C-141 Starlifter. Lockheed's design was chosen, and General Electric developed the TF39 engine specifically for this aircraft. Boeing, having lost that competition, incorporated elements from its submission into what would become the 747, following a request from Pan American World Airways President Juan Trippe for a large-capacity passenger jet.
The Boeing 747 was produced in multiple variants over more than five decades. Most models retained similar dimensions until the introduction of the 747SP, which was shorter to improve range. The most significant changes came with the final variant, the 747-8, which featured an extended fuselage, enlarged wingspan, new engines, and increased maximum takeoff weight (MTOW).