MAC-L24B a fictional repaint for the Lear Jet 24B to represent the Lear Jet 35 - C-21A, used by the U.S. Air Force.
From Wikipedia: The Learjet Model 35 and Model 36 are a series of American multi-role business jets and military transport aircraft manufactured by Learjet. When used by the United States Air Force they carry the designation C-21A.