Why do passenger planes fly slower than they used to?

Flying is now more comfortable, safer and more efficient than ever before – but one thing has changed over the years: speed. If you travelled in a Boeing 747 in the 1970s, you often reached your destination faster than you would in a modern long-haul jet in 2025. So why are passenger planes slower today than they used to be? Is it the technology, the airlines or simply economic efficiency?

Christoph Regli, head of the aviation programme at the Zurich University of Applied Sciences (ZHAW) and an airline pilot, explains that it is not just a question of what is technically feasible, but also of economic and ecological considerations.

‘Faster aircraft are much more complex to build – you are welcome to take a look at the two Concordes in the Musée de l'Air et de l'Espace in Paris Le Bourget,’ he says. Indeed, Concorde's extreme speed posed major technical challenges. The aircraft's nose heated up to over 120 degrees Celsius at twice the speed of sound, causing the fuselage to expand by almost 18 centimetres. ‘As you can imagine, this posed significant challenges for the construction of such fast aircraft,’ says the expert.

Flying slower, travelling more efficiently

The Airbus A350 can theoretically reach up to 90 percent of the speed of sound, but in practice, it is flown significantly slower—primarily for reasons of efficiency. 'Both economic and ecological considerations factor into the chosen cruising speed,' explains Regli. Depending on wind conditions, air pressure, and temperature, flying at a reduced speed can lead to substantial fuel savings—benefiting both airlines and the environment.

Fuel is not only the largest cost driver for airlines, but also a significant source of CO₂ emissions. ‘So both cost pressure and environmental considerations lead to lower cruising speeds,’ says the aviation expert. Lower speed also means lower engine load, which has a positive effect on maintenance costs and noise emissions.

The aviation industry is increasingly turning to modern engines designed to optimize fuel efficiency. One such innovation allows different engine components to operate at precisely matched speeds. 'This technology makes it possible to reduce fuel consumption without requiring aircraft to fly even more slowly,' explains Regli. As a result, cruising speeds are unlikely to decrease further in the long term.

Is supersonic flight making a comeback?

Despite the focus on efficiency, some companies are once again developing supersonic jets. One example is the Overture from Boom Supersonic. But Regli remains sceptical: ‘This product will presumably be positioned in the premium segment as a niche market, and the question of whether it can meet environmental requirements remains unanswered,’ he says. In addition, these types of jets pose a challenge for air traffic control, as they have to be guided past normal commercial aircraft.

‘For most shorter flights, the time taken to get to the airport, check in baggage, go through security and get to the gate is longer than the time saved by a slightly increased cruising speed,’ says Regli. ’I think that we still have a great deal of untapped potential in this part of the flying experience.’

His conclusion is that if you're on a plane, there's little you can do to influence the time—so you might as well relax and switch off.  ‘Let's enjoy the extra minutes in the aircraft, where we can feel safe, be pampered by the cabin crew and not constantly disturbed by e-mails or phone calls!’