the nature of united technologies  8 united technologies corporation The PW4000 proves daily that it's among the safest, most reliable engines for airlines around the world. Among engines that power the Boeing 777, the PW4000 has the lowest in-flight shutdown rate and fewest engine removals. It is the first engine to be certified for 207-minute extended-range, twin-engine operation. Its continued reliability is recognized by airline customers around the world, including All Nippon Airways.