Learjet 40 airplane model. The Learjet 40 is a light business jet produced by Bombardier Aerospace. The Learjet 40 is derived from the Learjet 45, but with a shorter fuselage, and is powered by two Honeywell TFE731-20AR engines. These are known as the "AR" engines. The 40 model takes place of discontinued light Learjet 31a in Learjet model line.