A plane’s velocity is constantly changing, influenced by factors ranging from its altitude and weight to the surrounding atmospheric conditions. The speed that determines how quickly you arrive at your destination is often very different from the speed the aircraft needs to maintain flight.
The Standard Cruising Speed
International commercial jets typically settle into a cruising speed that represents the most efficient balance of time and fuel consumption. This optimal velocity for long-haul flights generally falls within the range of Mach 0.80 to Mach 0.85, translating to approximately 550 to 600 miles per hour (mph) at high altitude. Modern widebody aircraft, such as the Boeing 787 and Airbus A350, often operate efficiently at the higher end of this range. Aviation professionals use the Mach number to measure speed because it is a ratio relative to the speed of sound, which changes with temperature and altitude. This speed range is chosen because flying faster dramatically increases aerodynamic drag, while flying slower extends the flight duration too much, making the overall operation less economical for the airline.
Airspeed Versus Groundspeed
Airspeed is the speed of the aircraft relative to the mass of air moving around it, and this is the measurement that determines whether the wings are generating enough lift to keep the plane flying. Groundspeed, by contrast, is the speed of the aircraft relative to a fixed point on the Earth’s surface, which dictates the flight’s duration and arrival time. The difference between these two measurements is the wind speed and direction. A simple analogy is a person walking on a moving walkway at an airport; the person’s effort (airspeed) remains constant, but their speed relative to the terminal floor (groundspeed) changes depending on whether the walkway is moving with or against them.
The Impact of the Jet Stream
The most significant external factor causing a difference between airspeed and groundspeed is the jet stream, a powerful, fast-moving current of air found at high altitudes where commercial planes cruise. These currents can reach speeds well over 100 mph and are typically found flowing from west to east across the globe. Pilots strategically utilize these streams to their advantage on long-haul routes, especially those crossing the Pacific or Atlantic oceans. When a plane flies with the jet stream, it experiences a strong tailwind, which directly adds to the aircraft’s groundspeed, allowing it to cover ground much faster than its internal airspeed suggests. Conversely, flying against the jet stream results in a headwind, which subtracts from the groundspeed, forcing the plane to take a longer time to reach its destination.
Speed During Takeoff and Landing
The speeds used during the initial and final phases of flight are significantly lower than the cruising velocity, prioritizing safety and control over efficiency. During takeoff, a fully loaded commercial jet must accelerate to a speed sufficient to generate the necessary lift, typically reaching between 160 and 180 mph before rotating off the runway. This speed varies based on the aircraft’s weight, the runway length, and atmospheric conditions like air density.
The typical landing speed for a large commercial airliner is in the range of 130 to 160 mph. Furthermore, aviation regulations impose a speed limit of 250 knots (approximately 288 mph) for all aircraft operating below 10,000 feet above mean sea level, ensuring safety and providing pilots with more time to react to other traffic in congested airspace near airports.