I had a flight from London to DC.
At take-off, the pilot warned that as we crossed the airport boundary he would have to throttle back, and even though it might feel like we were about to fall out of the sky, we would not. He was right, that was exactly what it felt like.
Stayed subsonic until over Past Ireland, then it went supersonic.
You could feel a thump in your back as the pilot flipped the switch on the after burner for each engine.
The Mach indicator on the bulkhead started climbing quite rapidly. Noise level was no more than a normal plane.
Once at altitude (60,000') there were a few things to notice.
One was the slight curvature of the horizon. Another was the paint slowly going dark as it heated up.
In a normal plane, if you lean against the window, it is usually very cold - these were very HOT.
Normally, at 30k' the clouds below move by quite slowly, now looking down on the clouds twice as far (or more) below, they were really whizzing by.
The interior was small/narrow by modern plane standards. Seats quite nice. but not up to first class standards - but that was less important because you wren't sitting in them for as long.
The flight was over much too fast.
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Anyone wondering how I got this flight: I was flying business class from Paris to Boston.
Got to London, and my flight had been cancelled. Stood in line for reassignment ... two guys (American) in front of me were giving the ticketing agent a hard time.
Can't say I really blamed them, he was moving them from business non smoking directly to Boston into peasant class/smoking on a flight to NY with connecting flight later in the day.
My turn came, and I took pity on the agent - it wasn't his fault after all. So said "My flight seems have been cancelled, can we find anything to get me to Boston?" He looked up from his screen and smiled - I think I was the first to not scream at him or something. Anyway, he rattled a few keys and said "Hmm.. looks like the best I can do is flight to DC with connection to Boston ... the only thing is, the flight to DC is on Concorde ... is that ok?". I thought about it a few seconds, and said "I think that should work". Concorde ticket issued.
The only thing that sort of spoiled the trip a bit was that United (the connecting flight) "lost" the pilot ... don't ask me how ... and it took them four hours to find another.