The LearJet family began with the original six to eight seat Lear Jet 23 which first flew on October 7 1963. The diminutive Model 23 pioneered an entirely new market segment for private jet charter, and proved very successful in that endeavor as it was able to transport up to 8 people without sacrificing comfort or style. The first production 23 was delivered in October 1964, but after a total of 105 were built by 1966 – they would be replaced by the improved Lear Jet 24 for those who sought more range and power than what had been offered before. These jets increased engine horsepower output from 3200 hp (3120 kW) per side powering just one compressor stage each at takeoff rating; ultimately offering 6400-8000hp/side depending on mission requirements!