The NTSB said it is now leading the investigation into the July 10 Ryanair flight after determining the window blowout happened in Greek airspace, with Greece participating in the probe.
A 61-year-old man was partially sucked out after the window dislodged minutes after takeoff from Thessaloniki, suffering neck and shoulder injuries and friction burns before other passengers pulled him back inside.
Flight data show the Boeing 737-800 climbed past 15,000 feet about six minutes after departure, then dropped to roughly 6,000 feet and stayed low for about 30 minutes before returning to Thessaloniki.
The NTSB has said it was notified of both a right-engine issue and cabin decompression, while Ryanair has publicly repeated only that the flight turned back after a window became dislodged.
Videos shared by Greek media showed oxygen masks deployed and the damaged window, while an aviation expert said such rapid-decompression events are rare but seat belts can be critical in the first seconds.