Why is commercial air travel still the same speed it was 60 years ago? And will it ever change?



Why is commercial air travel still the same speed it was 60 years ago? And will it ever change?

In: Technology

Because breaking the sound barrier is difficult and eats up A LOT of fuel. There were a few attempts at supersonic airliners, but it turns out nobody really wants to pay 5 times the price to get to their destination twice as fast.

So now commercial airliners focus on efficiency, rather than speed.

It did get faster, we had the Concorde, which was super sonic and heinously expensive to operate.

That’s really what it is. We’ve optimized aircraft from a cost vs speed perspective. Can we go faster? Hell yea. Is it cost effective or affordable? Not really.

Source: am an aerospace engineer

Travelling faster requires a lot more energy and that means more fuel, it is possible to build an aircraft surpassing that of Concorde, but it would be expensive to build an operate and the demand for very fast aircraft isn’t there.

>Why is commercial air travel still the same speed it was 60 years ago? And will it ever change?

Supersonic commercial flight was [tried out](https://en.wikipedia.org/wiki/Concorde), didn’t prove to be in enough popular demand to be deemed profitable and was abandoned again.

Commercial jets cruise just below the speed of sound.

Going any faster requires a supersonic aircraft, which radically changes the aircraft design and fuel consumption and is much more expensive.

There were some forays into supersonic passenger travel, but the cost was never competitive and the earth-shaking sonic booms of Concorde jets leaving the airport were very unpopular.

It’s actually faster now because we have more direct flights to places. For example, Delta Airlines, who used to be the ‘route everything through Atlanta’ airline, now has lots of direct flights from multiple mini-hubs.

The planes themselves can’t go any faster without creating sonic booms which they aren’t allowed to do over land

[Because transonic drag (Mach 0.8-1.2) is awful](https://upload.wikimedia.org/wikipedia/commons/0/0e/Qualitive_variation_of_cd_with_mach_number.png)

Around 80% the speed of sound the drag on the plane starts to skyrocket, going from 80% to 90% can be a 3x increase in drag which results in a 3x increase in fuel consumption which results in a massive increase in ticket cost. Once you get beyond about Mach 1.2 though drag starts to drop off.

This region between Mach 0.8 and Mach 1.2 is the transonic region and its when some of the airflow is supersonic (pinch points and tight curves on the plane) while others parts are subsonic and it creates this real mess. This is why planes either fly well under Mach 1 or well over.

Jet airliners have been running in the Mach 0.75-0.85 range for over 60 years now, that’s as high as they can practical go without breaking the sound barrier which is a no-no over land, that’s why they’ve instead been focused on fuel efficiency to reduce running costs

There is research into Quiet Supersonic jets but its still quite experimental and a few decades off. Until we can get rid of the damaging sonic boom overland flights have a pretty firm limit at Mach 0.85

The problem is that we started to approach the sonic barrier. The effects of the speed of sound starts to show itself in some areas at around 80% of the speed of sound. This is because the air needs to move around the aircraft body and the wings and may therefore have to go faster then the speed of sound in certain places. The problem is that when you start getting these areas of air going faster then the speed of sound you start getting a layer of high pressure air clumping up in front of the aircraft. At lower speeds this high pressure air will be able to move forward away from the aircraft but not when you start getting towards the speed of sound. The problem is that this high pressure air is pushing the aircraft back. That creates a lot more drag then normal flight. You therefore need a lot more power and use a lot more fuel to fly closer to the speed of sound. And is there anything commercial air travel does not like it is to use more money on fuel.

At around 80% the speed of sound is usually the most fuel efficient speed. Fly slower and you have to spend more fuel because the flight is longer and fly faster and you have to spend more fuel because of the increased drag. There are a few aircraft that is designed to fly faster. Of course the Concorde was designed to fly faster then the speed of sound. By going faster then the speed of sound you get rid of a lot of the issues with drag however you still need to use about twice the fuel in normal cruise and a lot more fuel punching through the sound barrier. So the Concorde was very expensive and required big fuel tanks compared to its small cabin. The price was not really its problem as its clients were not looking at the price themselves, however the cabin size was a problem. But there are a few private jets which can go faster then most commercial airliners. There are several that goes about 90% the speed of sound and a few planned ones designed to go supersonic. But these do require people who are rich enough to want to spend the massive amounts of money on fuel at these speeds.