Mileage Plan started in June of 1983 under the name "Gold Coast Travel Plan". Perhaps we might see some sort of Mileage Plan 20th anniversary promotion next June.
Jeffrey Pinneo, now CEO and President of Horizon, was supposely "responsible for the original implementation" of the Gold Coast Travel Plan.
http://www.alaskasworld.com/Newsroom...131_091446.asp
The first frequent flyer program was American's AAdvantage program launched in May of 1981. United responded by announcing Mileage Plus a few days later.