National Airlines was one of the premier domestic airlines from the 1950s until 1980. Their profile and appeal exploded in 1958 when they were the first domestic carrier to offer jet service using the new Boeing 707 (Pan Am offered international flights to Europe on the 707). By 1964, they were the first American all-jet domestic airline.
National was the carrier you would take from Washington down to their hub in Miami for a nice warm weekend getaway. Or, prior to 1961, take a jaunt down to Cuba for a little R&R.
By the late 1970s, they were an acquisition target and globally dominant Pan Am looked to merge National Airlines’ operations into theirs to take over their lucrative domestic routes. In 1980, Pan Am closed the deal for the airline, and National Airlines ceased to exist.