World War II provided many technological improvements in flight, and commercial airplanes became faster and more efficient. This led to the creation of the coach class, which let people travel around the country for around 100 dollars, one third of the price of tickets in the 1940s.
From 1950 to 1958, annual boarding more than doubled from 17.3 million to 38 million. Airports around the country needed to expand, and delays in luggage, take offs and even landings were commonplace.
Radar, a common fixture in today's commercial planes, was not widely installed until 1955. Beforehand, pilots only had a vague idea where other planes were, and had to use sight to get a location. In 1956 a TWA liner collided in flight with a United DC-7, killing 128 people. Afterwards, Congress passed the Federal Aviation Act of 1958, requiring air traffic to be monitored by radar at all times.
