An upgrade to the General Electric J85 engine in U.S. Air Force T-38 trainers has led a Denison, Texas firm to launch a “total upgrade” for Learjet 23s, 24s and 25s, whose GE CJ610 powerplants are a civilian version of the J85 military engine. The program is being offered by Best Jets, a new company established by the owners of Best AeroNet fuel brokers at Grayson County Airport. The cornerstone of the engine improvement is a new GE spooled rotor “drop in” replacement for the disk and spacer design. Best Jets said the mod will double the engine’s TBO to 10,000 hours and triple the hot-section inspection interval to 3,000 hours. The upgrade program also includes installation of RVSM-certified avionics, interior refurbishment, new paint and a Stage 3 hush kit. All-up cost is estimated at about $2.5 million.