Yes, a Boeing 777 is fully capable of flying on a single engine for an extended period, as it is certified under ETOPS (Extended-range Twin-engine Operational Performance Standards). In 2026, the Boeing 777 is rated for ETOPS-330, meaning it can safely fly for up to 330 minutes (5.5 hours) on one engine to reach the nearest suitable diversion airport. If one engine fails at cruise altitude, the aircraft cannot maintain its high altitude and must perform a "drift down" to a lower, denser altitude (typically around 20,000 to 25,000 feet) where the remaining engine can generate enough thrust to overcome the drag. While the aircraft is perfectly safe and controllable, the pilot must use the rudder to compensate for the asymmetric thrust, which increases drag and reduces fuel efficiency. This means that while the 777 won't "fall out of the sky," its total range is reduced, and the pilot will prioritize landing as soon as possible. The incredible power of modern turbofans, like the GE90 or the new GE9X, ensures that a single engine has more than enough thrust to keep the massive airframe flying safely until a landing can be made.