35,000 ft in a VII

[Hagar]

I've seen reports of fighters coming within a whisker & maybe even exceeding Mach 1 in a dive. Most, if not all, happened by accident & some pilots did not survive to tell the tale. The control reversal phenomenon made it very difficult to recover even if the aircraft did not break up or suffer severe damage. As I understand it, none of this could be officially confirmed as there was no way of accurately measuring it.

[fido]

Pippin,  I suppose you mean in controled flight?  I would think that airflow compressibility would become a factor.  I kind of understand what it does, but not why it does what it does.  If a propellor driven craft did break the sound barrier I would sure be interested in the details.

Fido

[HawkerTempest5]

The RAF carried out tests and trials during WW2 with Spitfires and Tempests and anything big and fast to study the effects of compressability and to see if they could go Super Sonic. Most broke up I think.
There are reports of the ME 262 breaking the sound barrier also, but most people think this unlikely.

[Wing Nut]

Considering the reports of how fragile that plane was, I would doubt it very much.  All you had to do was spit on it and it would break...