American Airlines asked Convair to design an aircraft for coast-to-coast flights, able to fly nonstop New York to Los Angeles against the wind. They wanted somewhat larger passenger capacity than the 880, which was the smallest of the first-generation U.S. jet airliners. The 990 entered production in 1961. Some call this the Golden Age of Airliners while others say this was the sexiest airliner ever. :)
A Boeing 707 flying over the Golden Gate Bridge, 1958.