What was the first jumbo jet built?

The first jumbo jet built is widely recognized as the DC-10. This aircraft revolutionized air travel when it entered service in the early 1970s, offering significant capacity for passengers and cargo compared to its predecessors. The DC-10 was designed as a wide-body aircraft, which allowed for a more spacious cabin layout and greater efficiency in long-distance flights.

The DC-10's unique design included a tri-engine layout, with one engine mounted on the tail and two under the wings, which contributed to its distinctive appearance and operational capabilities. It became known for its ability to meet the growing demand for higher passenger capacity on international routes, effectively marking the beginning of the modern era of long-haul travel.

In contrast, the other aircraft listed do not meet the definition of a "jumbo jet." The Boeing 727, while also an important aircraft in commercial aviation history, was not classified as a jumbo jet because it is a narrower body and smaller in capacity than the DC-10. The P-51 is a World War II fighter aircraft, and the U-2 and SR-71 are reconnaissance aircraft used primarily for military purposes, further highlighting the DC-10 as the first true jumbo jet due to its design and impact on commercial aviation.