The Learjet 45 (LJ45) aircraft is a mid-size business jet aircraft produced by the Learjet Division of Bombardier Aerospace. The Model 45 was the first all-new design since the original Learjet, and significantly altered the Learjet line. Through its four primary variants – the original Model 45, the Model 45XR, Model 40 and Model 40XR – it was the Learjet Division's principal product from the 1990s until the introduction of the Model 75 variant in 2012.