If you have been following aviation news, then you might have come across Boom – a company that is looking to design the next commercial, supersonic aircraft. Their last test flight took place in January 2025 and by all accounts was fairly successful. And they aren’t the only team looking to bust the sound barrier for commercial flight – NASA’s QUESST project is looking to redesign aircraft to try in order to aerodynamically reduce the boom to more of a bump.

The NASA X-59 flew on June 5, 2026, and reached Mach 1.1 (around 713mph) during its 81 minute test flight from Edward’s Air Force Base. This was at an altitude of 43,400 feet which is the top end of where current commercial aircraft tend to fly – the A380, Boeing 787, A350 have a maximum ceiling of 43,100 feet*. Later the same month it headed up even higher – reaching 55,000 feet where it achieved Mach1.4 which is within the parameters at which its sonic ‘thump’ can be properly tested at.

*In case you’re wondering why there is a seemingly arbitrary 100’ added in there, this is because the maximum operating altitude is the maximum useable altitude aircraft can go up to. Not that we often do, but in theory we can, which means it must be practical – having a hard cut off at 43,000’ to the foot would not be. While autopilots are exceedingly good at maintaining an altitude, fluctuations and disturbances in the air do buffet the aircraft around enough for a few feet this way or that around the set altitude. So, an extra 100’ is added on to make the maximum level useable. And yes, if you get a TCAS telling you to fly up, then fly up you must – the aircraft won’t fail structurally or aerodynamically if you exceed the maximum operating altitude because there are margins built in. You would however find yourself approaching a point where the minimum speed starts to equal the maximum speed, and you would have to descend fairly rapidly once clear of traffic.

OK, enough on that and back to these supersonic aircraft. While supersonic commercial aircraft are once again on the horizon, a major hurdle still remains – regulations. These particular ones are not simple, box ticking things either, they have been in place for decades (for good reason) and removing them is intrinsically linked with the redesign f the aircraft structure itself.

Let’s head back in time to see how all this came about.

1947

First up, we head to 1947 and the sweltering Mojave desert.

This was a big year for the world. India and Pakistan gained Independence. “Something” crashed in Roswell. Oh, and Chuck Yeager went faster than any human had gone before, breaking the sound barrier in a Bell X-1 rocket plane.

‘Glamourous Glennis’ was dropped from the bomb bay of a B-29 Super fortress at around 30,000 feet. This was a safety thing – having the aircraft takeoff and climb up itself would have required a very large load of volatile rocket fuel, burning in an equally volatile system. So, she was dropped at an already high altitude, and then ‘rocketed’ up, literally, to 43,000 feet. Yeager noted that the Machometer jumped from 0.96 Mach to 1.06 Mach. He also recalled “There was no buffet, no jolt, no shock. Above all, no brick wall to smash into. I was alive.”*

*Yeager achieved this milestone while flying with two cracked ribs. I currently have a sore neck and am considering whether or not to go to work where, if I do, I will just sit there straight and level for a few hours. They were made of different stuff back then.

Anyway, point is he barely felt it, but those on the ground did. They were watching from Rogers Dry Lake in the Mojave desert and heard and felt a sudden, sharp double crack that reverberate cross the desert.

1963

Fast forward a decade or two, and while military aircraft have now been achieving more than Mach one for sometime, commercial aircraft are still slow old things. The USA is a big country and folk want to get around fast, so the FAA initiated the U.S. Supersonic Transport program, with the plan of developing a Mach 2 (or more) intercontinental, 300 seater passenger aircraft.

At the same time NASA started researching what the booms would mean for people living under the intercontinental paths. While military jets could boom away as they needed, it wasn’t needed all that often but if commercial aircraft were crisscrossing the continent all over the place, it made sense to see how those reverberating cracks might affect folk. They first experimented on the townsfolk of St. Louis, Missouri – booming above them and then asking them what they thought of said sound. Ninety percent heard it and just three percent were annoyed by it. So far so good.

In 1964, they did another experiment, this time over Oklahoma City, Oklahoma, and they interviewed three thousand of the city’s residents. Seventy-three percent reportedly responded that they could “live with the boom”, but forty percent said they thought it probably did some damage to buildings. Further experiments demonstrated that booms could cause rattling windows, cracking plaster and tiles, general building shaking, and while people said they could live with the sound, they also used words like “annoying”, “irritating” and “disturbing.” I repeat – people back then were made of stronger stuff, and possibly were also a lot more polite. Nowadays I think some somewhat more choice words would probably be used in place of “disturbing”…

Anyway, it made everyone realise that between the public disapproval and potential safety concerns, going supersonic over populated areas possibly wasn’t the best idea, and so…

1971

…in 1971, the FAA formally banned it.

This didn’t put a stop to commercial supersonic flight though. As we know, Concorde operated from 1976 to 2003, heading between Europe and New York. It just wasn’t allowed to go supersonic until it was over the water.

2014

In 2014, the FAA reviewed these regulations again. The review was not particularly successful because they were still unable to really account for annoyance and disturbance levels on the ground, and so the ban remained.

2026

We are back in 2026 now, and the FAA are reviewing a new proposal regarding supersonic flight, and this time it looks set to go ahead. If it does, it will allow aircraft to once again fly at supersonic speeds over land.

Let’s take a look at how it will work.

How it will work

The proposal will limit aircraft to an overpressure of 0.11.

What is that?

Well, it is the sudden and sharp increase in air pressure above the normal surrounding atmospheric pressure when an object beats the sound barrier. Normal atmospheric pressure – so you can think of that as the air pushing on you – is around 2,116 pounds per square foot at sea level. When an aircraft goes supersonic, it creates a shock wave of compressed air and overpressure is how much above the normal pressure that air spikes to.

Great, so 0.11 isn’t a whole lot?

Well, this is where people are concerned because while it doesn’t sound like a whole lot, it also doesn’t really equate to any useful measurement of how much disturbance it will cause on the ground. Overpressure only measures the amplitude of the noise signal. It doesn’t consider how humans would be impacted by it, nor by the frequency or rise time or signature length… Basically, it doesn’t measure loudness or impact on human irritation levels in any way.

Which is what the regulations were put in place for in the first place, and which is why subsequent attempts to review and remove them have been unsuccessful.

Reducing the boom

We also have to understand what the main method for reducing the boom is, because measuring overpressure does not entirely give a picture of the acoustic characteristics of this method, and more importantly the method does not always necessarily work.

The approach NASA and presumably Boom are going for uses the concept of Mach cutoff. When operating the aircraft at Mach cutoff, the sonic waves bends upward and the caustic line – where they crowd together and become concentrated – is directed away from the ground. Beyond this ‘carpet’ there is a shadow zone of nice, quiet, boomless serenity where only low level “evanescent waves” – which NASA claims are similar to background street noise levels – are heard. The big old boom is not.

Achieving this carpeting effect relies on quite specific aircraft speed, mass, altitude and atmospheric conditions, amongst other things, though. In the right combination, these cause the sonic boom to refract across the atmospheric layers and it does not reach the ground at anywhere near full intensity.

Aircraft speeds of around 110-113% the speed of sound provide the most success (and that is where the 0.11 overpressure rating comes in), but the environmental and operational envelope for getting it right is pretty narrow, and the success of it is sensitive to the smallest changes in speed, altitude, temperature, wind vectors and humidity. When they say sensitive, according to researchers, that can be as small as a 1% change in speed or heading and I know you’re thinking “keep it steady then” but the slightest turn, bump, or wind shift could adjust things enough to potentially prevent it working as planned.

So, when it works it is great, but get it wrong and rather than refracting the wave away, it can concentrate and merge everything resulting in amplified intensity. This would lead not just to a regular boom, but to one which can be up to five times greater.

So…

So we have a method of reducing the boom, but it requires very specific conditions and when not met, can result in far bigger, badder booms. And on top of that, our method for measuring boom induced human irritation levels is not really very accurate, leading to concerns that regulation removal is being rushed without proper review.

And….

And designers still haven’t managed to make these innovative aircraft very fuel efficient. Boom’s Overture aircraft is expected to burn around seven times the fuel per seat of a comparable, current commercial aircraft. That is expensive, and also not very environmentally friendly given it will lead to as much in increased C02 emissions. It will also produce greater pollutants like nitrogen oxides, black carbon and water vapour (which leads to contrails which leads to increased warming effects).

So…

The FAA proposal for a new supersonic ruling can be read here, and the plan is to finalise it in 2027, but while the future of supersonic air travel is coming (again) soon, and this is great news, it still needs a lot more study.

Right now, it appears it might be booming, but in the wrong way, and more research, public input and potentially technological innovation might well be needed before it really flies.