The world fleet of some 13,000 TPE331 turboprop engines has logged more than 100 million hours, Honeywell says. The TPE331 entered service in 1965, and has been shipped on 40 different aircraft types for regional airlines, utility, business and general aviation, and agricultural applications. Honeywell offers upgrade kits "for every key TPE model," said Laurena Ketzel-Kerber.