How fast does a plane really fly? It’s a simple question, but without a simple answer: How fast does a plane really fly?
Believe it or not, pilots rely on several speeds during flight. There are generally four different speeds that measure different things and are affected by different atmospheric conditions.
Before we jump ahead, let’s get two obvious facts out of the way. First, the aircraft travels at different speeds depending on the phase of flight. Second, different types of aircraft are capable of traveling at different speeds.
How fast is the plane in the air?
Airspeed is measured in knots. One knot equals 1 nautical mile per hour. One nautical mile is 1.15078 statute miles (commonly known as a mile). So 1 knot equals 1.15078 miles per hour.
The simplest type of airspeed is indicated airspeed, which is directly derived from the aircraft’s pitot-static system.
When an aircraft is flying or hurtling down a runway, the air is forced into the hole of the pitot tube and is measured, while static pressure measures just that – static air conditions. The indicated airspeed is simply calculated by measuring the difference between the dynamic pitot pressure and the static pressure.
But that’s not the most accurate metric once the plane is in the air. Different temperatures, atmospheric pressure, and other factors mean that this airspeed must be converted to something more realistic and usable at higher altitudes.
Actual airspeed adjusts the indicated airspeed for a number of factors. Most importantly, it adapts to the temperature and pressure at higher altitudes — as the plane climbs, the temperature generally drops and the air pressure always drops. Once we’ve made these adjustments, think of true airspeed as how fast the air is moving over the airplane’s wings at a particular altitude.
Pilots actually rely on a different type of speed during the cruise — and technically, it’s not speed at all. Mach number is the ratio of the actual speed of air to the speed of sound and is greatly affected by atmospheric conditions, especially temperature. It is a highly precise way of fine-tuning the speed in a specific area and is the unit that air traffic controllers use to separate traffic at higher altitudes.
Some typical air speeds
Boeing 737 NG/MAX: Mach 0.78, true airspeed of about 450 knots.
Airbus A320 series: Mach 0.78, true airspeed of about 450 knots.
Boeing 787 Dreamliner: Mach 0.85, a true airspeed of about 488 knots.
Airbus A350: Mach 0.85, a true airspeed of about 488 knots.
Airbus A330: Mach 0.82, a true airspeed of about 470 knots.
Boeing 757: Mach 0.80, true airspeed about 461 knots.
Concorde: Mach 2.02, a true airspeed of about 1,176 knots.
What is the average ground speed of an airplane?
Finally, ground speed is perhaps the simplest of speeds. It is the speed of the aircraft over the ground that adjusts for wind and altitude. For example, if an A321 has a true airspeed of 460 knots (529 mph), but is flying from New York to Los Angeles during the winter when headwinds can be very strong, the true ground speed will be lower. If facing a headwind of 100 knots (115 mph) – which is quite possible at that time of year – its true ground speed would be a glacial 360 knots (414 mph) and you’d be in for a very long trip to the west coast. Still, the Mach number would remain unchanged because the actual airspeed did not change.
Since an aircraft’s ground speed is strongly influenced by the winds it encounters in the air, no ground speed is associated with individual aircraft types. As a general rule, an aircraft’s ground speed can be anywhere from 350 knots (in a strong headwind) to 550 knots (in a strong tailwind). Of course, there are outliers. Every winter there are frequent stories of airplanes encountering very strong tailwinds while flying east over the Atlantic Ocean. Sometimes these speeds are higher than 700 knots or 805 mph. These planes don’t actually fly faster than normal – in fact, some might even slow down to save fuel due to strong winds. However, by harnessing the wind, they are able to travel at incredibly high speeds.
Of course, westbound planes are not so lucky. Dispatchers often plan a circuitous route—one that’s a longer distance—for these planes to avoid strong headwinds. Traveling a longer distance pays off because the plane saves more fuel than it would with a more direct route that takes the plane directly into the wind.
Bottom Line
There is no easy way to answer how fast a plane flies. But for the flying public, ground speed is probably the easiest answer. It’s about how fast your flight travels directly over the ground and has the biggest direct impact on 8888.