(Dallas, TX) — The co-founder of Southwest Airlines has died.

Herbert Kelleher used a cocktail napkin with co-founder Rollin King in 1966 to brainstorm a low-fare airline that revolutionized the industry with a fleet of 737’s.  The airline started out flying only in Texas but slowly expanded.  Southwest now flies more than 750 jets to 99 American cities and ten international destinations.

Kelleher was 87 and the airline did not reveal the cause of his death.