Did British Airways Wednesday New York – London Departure Go Supersonic!?

The Daily Mail reports on BA114. The British Airways 777 hit 745 miles per hour — BA’s call sign isn’t “speedbird” for nothing!

What’s more, the flight was reported to have flown at speeds of 745mph relative to ground speed.

The speed of sound at sea level is 761mph.

Several flights are reported to have made the journey from New York to London yesterday in around five hours 20 minutes due to the 200mph North Atlantic jet stream.

I’m not an expert on such things, but I believe that sound travels slower in air than at sea level. I’ve googled references to the speed of sound ‘on earth’ being 750 miles per hour. The Daily Mail claims that this Boeing 777 at 745 miles per hour exceeded the speed of sound. Perhaps knowledgeable readers can weigh in on whether this claim is, in fact, correct.

Or more specifically whether the plane flew at a speed equivalent to the speed of sound on the ground (which appears to be a different matter from actually saying, as the Daily Mail does, that the plane went supersonic).

Regardless, it was a fast Eastbound flight, oddly though not making up most of the time of its departure delay. I sure hope crew finished their service quickly, because it doesn’t leave much time for sleeping.

Fast as this is, it’s not nearly as fast as the Concorde was.. it used to make the journey in about 3 and a half hours and set a record for the journey at under three.

The winds supporting high eastbound speeds, of course, slow down aircraft flying Westbound (or cause them to fly around these heavy winds causing longer flight times). I don’t think I’d want to fly taking a 757 Westbound across the Atlantic this week (unless I’ve never diverted to Goose Bay or Gander and wanted an increased likelihood of doing so).


About Gary Leff

Gary Leff is one of the foremost experts in the field of miles, points, and frequent business travel - a topic he has covered since 2002. Co-founder of frequent flyer community InsideFlyer.com, emcee of the Freddie Awards, and named one of the "World's Top Travel Experts" by Conde' Nast Traveler (2010-Present) Gary has been a guest on most major news media, profiled in several top print publications, and published broadly on the topic of consumer loyalty. More About Gary »

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Comments

  1. Yes – the thinner the air, the higher the speed of sound through the air.

    But, the plane didn’t break the sound barrier – ground speed doesn’t matter, air speed matters. Many planes exceed the speed of sound at sea level in calm air, while they’re at 38k feet with tail winds.

  2. This whole line of reporting is dumb. “Supersonic” would be relative to the speed of sound, but wind affects sound just as it does the plane, and the plane is moving at normal plane speed relative to the air, not supersonic speed.

  3. You say it made up most of its departure delay, but from what I see there it left 80 minutes late and arrived 80 minutes late. What gives? Long taxi time perhaps?

  4. The answer to Gary’s question is, I believe yes. The plane was travelling at or near the speed at which sound travels on the ground in normal conditions, but as compared to sounds in the same general area as the plane in the same jetstream it was going slower because they were going slower. Other than that, it’s all relative. Imagine a source of sound in the plane, like a mouth speaking. Within the plane, that sound wave travels at the normal speed of sound. That’s why you can hear it undistorted. But to a stationary observer outside the plane, the sound travels towards and away from her at the speed of sound plus (or minus depending on direction) the speed of the plane. It’s like throwing a ball 5 mph forward in a car moving 40 mph. To the guy catching it in the car it’s going 5 mph. To a guy on the street it’s going 45 mph. (This is why light is fascinating. It goes at the same speed relative to everybody, the guy in the plane, outside the plane, in the car or on the street. But sound is like the ball not like light.)

  5. Simply put: To break “the speed of sound” you must use the airspeed, not the ground speed. Tail winds and head winds are not included in any calculation of airspeed. This is not just for reasons of nomenclature, but for all of the physical affects of speed (and when a sonic boom would happen, etc.)

    It is also true that the speed of sound gets slower and slower at higher [density] altitude. The Concorde flew at 60,000+ feet, which made it much easier to achieve Mach 2.02

  6. If the 200 mph Jetstream was directly on the tail, then 545 mph airspeed + 200 mph tailwind = 745 mph groundspeed. 545 mph airspeed is normal cruise speed for these jets, and is not close to the speed of sound.

  7. Okay guys — so at 30k to 35k feet cruising altitude and average humidity and pressure at that level – what is the average speed of sound barrier?????

    I think people are saying that 761 is barrier at sea level, and at altitude the barrier is <761 correct???

    So a plane flying over 761 mph should have broken it correct??

  8. There must be something in the air over the Atlantic. I flew JFK-TXL on 5 January and we were hitting about 740 mph for a while.

  9. As others have said, this aircraft definitely did NOT go supersonic. However, there is a bit of misinformation above, as the speed if sound is dependent _only_ on temperature. There is a standard model of the atmosphere in which the temperature of air decreases 6.5 degrees Celsius with every kilometer of altitude (up until 11km, which is basically the ceiling for modern airliners), and thus it is easy to determine the speed of sound at a given altitude based on this model. The real atmosphere varies from this idealized model of course, but the model is still fairly accurate. In any case, my point is that the speed is sound is actually LOWER at altitude than it is at mean sea level (340m/s at MSL vs. ~300m/s at typical cruising altitude). Despite the fact that the plane was traveling near the speed of sound _at sea level_, it did not exceed the speed of sound at its cruising altitude. Its mach number was most likely in the ~0.85 range, which is typical for airliners as mach number is relative to the surrounding medium.

    Additionally, I would be VERY surprised if a 777 could withstand supersonic flight. There are enormous pressures and stresses that arise when an airplane approaches and breaks the sound barrier, and commercial airplanes are not designed to withstand these. Supersonic aircraft have drastically different design characteristics meant to account for these pressures and stresses. Commercial aircraft designs, if they were able to withstand supersonic flight in their current form, would be extremely inefficient at supersonic speeds. Not to mention, the plane would probably break up! So let’s be thankful that this thing did not break the sound barrier, because if it did then we’d probably have a very different scenario on our hands.

    In short: this flight did not go supersonic… it just went really, really fast!

  10. Speed of sound varies by air density and so is not at all relevant to ground speed. They were not flying close to speed of sound for the altitude they were flying.

  11. I appreciate the information that you post so I clicked on your link for the CITI/AAdvantage CC application and applied for it so that you can get paid.
    I trust that the information you post is accurate so I did not bother verifying what you posted and went ahead and applied for the card.

    AFTER I was accepted by CITI, I was surprised to discover the following:
    1. On your website it said “Plus 2 Club Passes” – I didn’t see anywhere (after the fact) on the CITI website where it said I would get 2 Club Passes.

    2. On the AA website it said that you only have to spend $2000 in 3 months, but on the link you provided it said I have to spend $3000 in 3 months. So now I am locked into spending $1000 more than I would have if I had applied directly on AA’s website.

    3. On the AA website it says “$100 AA flight discount every card membership year”, but on your link it does not have this at all. I feel short changed by this.

    If your links offer different terms/benefits than applying directly with the airline, you should notify us of this difference.

  12. @Jason Flyer my blog posts had said 2 club passes, because that was the offer that Citi was making at the time but is one they announced was ending last week so I removed that from my site.

    My understanding is that the $100 flight discount — which only was available by meeting an annual spend threshold that it sounds like you don’t want to meet — is something Citi is pulling as well.

    I wasn’t aware of a $2000 spend offer until I posted the $3000 one. I got an email from Joe Brancatelli who found it as well, and he noted that he found it right after he published his own list of best current offers (which he does not get ‘paid’ for). I do my very best to be aware of all the offers that are out there but it’s possible that even checking on things when I see 50k offers, I may have missed the fine print on one that shows a lower spend requirement.

    If you feel like you were somehow disadvantaged by me, send me an email and I’ll see if I can make it up to you.

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