The Boeing 777, one of the world's most successful long-haul widebody aircraft, typically cruises at a speed of Mach 0.84. This is approximately 560 mph (900 km/h) at a standard cruising altitude of 35,000 feet. The aircraft has a maximum operating speed, known as MMO, of Mach 0.89. While it is technically capable of pushing slightly faster, flying at Mach 0.84 provides the optimal balance between fuel efficiency and flight duration. In 2026, the newer Boeing 777X (the 777-9) is entering wider service and maintains a similar cruise speed of Mach 0.85, using its advanced composite wings and GE9X engines to fly more efficiently at these high subsonic speeds. It is important to remember that "Mach" is a measure of the plane's speed relative to the speed of sound at a given altitude; therefore, the actual "ground speed" of a 777 can vary significantly depending on whether it is flying into a headwind or being pushed by a powerful jet stream, which can sometimes result in ground speeds exceeding 700 mph.