How well I recall the old "Military Standby" on US legacies. Good well into the 70s, wasn't it a "walk up" 1/2 of the regular coach? All it took was an ID, and the willingness to risk some unusual routing or having to wait over night for a connection.

A bargain back then, since the "fare spread" was not near so wide as today's highly varietal buckets in which no two people aboard a flight may have paid the same fare.