On Friday a flight-enthusiast passenger noticed that a Spirit Airlines aircraft that had taken off a few spots ahead of his United plane UAL was now well him, according to a flight tracker.
The passenger, who is also a licensed flight dispatcher, guessed that the Spirit flight was likely flying slower to save money, like a frugal driver on the highway. Fuel economy usually decreases at 50 mph according to the DOE. This interesting observation revealed an open secret in the world of airlines and flights: They don't all fly at the same speed. Two identical routes with identical weather conditions can have two different ETAs.
Despite the occasional pilot proudly informing passengers about an intention to make up extra time in the air, people generally assume planes are going as fast as they know best, like a speed limit, similar to a bus or a train. Even Scott's wife Kristina tweeted his surprise at this fact.
Bernstein account analyst Daniel Roeska told Yahoo Finance that these speeds all depend on the specific airline and its goals. Some airlines like Ryanair and Wizz fly typically at the optimum speed which reduces fuel burn en route, he said.
Network airlines sometimes fly faster to enable a higher productivity given that their planes are on the ground for a long time he said. If you fly slower, you can cram more flights into your day. However if you fly faster you could add less flights and fewer fuel costs. In other words, speed is dictated by the airline's goals, be they on time performance, cramming flights in or saving money on fuel — things that are all in flux depending on the airline, the day of the week and the situation.
The differences are not huge, Roeska said, usually something like 466 mph to 547 mph, which is the difference of covering 81 more miles in an hour.
Evaluating the Spirit and United situation, Mann said that normally airplanes looking to make up speed will fly lower in this case, but could be due to the United aircraft operating at a lower weight fewer passengers less cargo and fuel than the Spirit aircraft in the Airbus A380. This would make the Spirit plane slower to climb with a slower cruising speed, said He.
Airlines still try to save fuel when they can, he said The physics of flight is that flying faster and heavier at any given altitude requires greater fuel flow. Altitude is tricky since it s often a product of weight and Mann explained that long-haul flight flights often have to step climb, which is when a plane will slowly climb as it burns off fuel because the fuel itself represents a significant weight cost
They can't reach the final cruising altitude with their initial departure weight, he said, noting that electric planes will break down the air-playbook in the future since batteries don t burn fuel and become lighter, creating a challenge to electric propulsion.