What event marked the introduction of commercial air travel for the masses?

The introduction of the Boeing 707 is recognized as a pivotal moment that marked the beginning of commercial air travel for the masses. Launched in the late 1950s, the Boeing 707 was one of the first commercially successful jet airliners, making air travel more accessible and appealing to the general public. Its wide-body design and jet propulsion allowed airlines to offer longer routes and faster flying times, significantly reducing travel time compared to propeller-driven planes. This was crucial in transforming air travel from an exclusive experience for the wealthy into a popular mode of transport for average passengers.

The development of jet engines was important, as it laid the foundation for faster and more efficient air travel, but it was the specific application of those engines in the Boeing 707 that made a significant impact on commercial aviation. Other options, such as the Air Traffic Regulation Act and the launch of the Concorde, were influential in different ways but did not have the same immediate effect on the general public's access to commercial air travel as the Boeing 707 did.