Calspan Aerospace acquired this Learjet 24D in 1979. It was then modified into a variable stability aircraft and after completion in 1981 entered service first at the U.S. Naval Test Pilot School and the U.S. Air Force Test Pilot School. In October, 2017, Calspan acquired a Learjet 31A to be used as a new VSS (Variable Stability System) aircraft to replace the Learjet 24D which is now retired and stored behind the Calspan hangar at Niagara Falls International Airport (KIAG/IAG).