Today (8/25/17), AA 60 flight data showed that at one point the aircraft was operating at 682 mph at 35,000 feet. At that altitude, isn’t that dangerously close to exceeding the speed of sound?
Never mind. I just learned that breaking the sound barrier depends on air speed, not ground speed. If AA 60 had a large tail wind, it’s airspeed was probably not very close to Mach 1.
It’s too bad http://groundspeedrecords.com/ is down now, it had a lot of photos of high groundspeeds in various aircraft.
The site is up for me. The latest commercial speed they give is an A380 at 675kts=776mph