The most reliable reports seem to indicate it "only" hit Mach 0.98; It seems highly likely that there was supersonic flow over parts of the airframe at that speed, but the aircraft itself was not supersonic.

> When the airplane was approximately 150 nm northeast of Thunder Bay, Ontario

That’s the best place name for accidental supersonic flight, if you ask me.

Far away from people on the ground for when the wings rip off.

(As happened on a 767 in 1991 when a thrust reverser malfunctioned and deployed in mid flight, a problem that if not addressed within seconds is irrecoverable.)

https://www.youtube.com/watch?v=WsYU7tjOvm0

No one survived this accident, the worst aviation disaster in Thailand's history.