 The XR allowed a gross weight 1,000 pounds greater than the original Model 45, greatly increasing payload and fuel/range options.The aircraft also has exceptionally short runway requirements for mid-size bizjets, capable of loaded flights from 4,000-foot runways.The 45XR's performance and specifications increases are due to the upgrading of the engines to the TFE731-20BR configuration, flat-rated to 3,500 pounds thrust, even at 104 degrees Fahrenheit, well above the 88-degree mark for that power from the original Model 45's TFE731-20 engines.