 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.The Model 45 was developed in the 1990s as a competitor in the "super-light" business jet category, a rival to the popular Cessna Citation Excel / XLS – but sacrificing the Cessna's stand-up room for the Learjet family's traditional high-speed performance.The Model 45 was Learjet's first completely new ("clean sheet") design since the company's first aircraft (all other models having been evolved from the original 1963 Learjet design, the Model 23).