In the late 1960s, it became apparent to Lockheed that a gap existed in the market between the high capacity, intercontinental Boeing 747, and the older 707s and DC-8s. Medium range aircraft like the 737, 727 and DC-9 too small to economically service larger longer domestic US routes, and the Lockheed L-1011 TriStar developed to fill the gap.

A dual aisle would afford greater passenger comfort, and the ability to carry 250 to 300 passengers coast-to-coast in much greater comfort and with better economics than 707s and DC-8s opened the market for Lockeed’s new tri-jet, which would also face competition from the similarly designed Douglas DC-10.