Quite interesting, but I do not think the article leads to such =
conclusion. Think about it: several types of aircraft have been flying =
very high above mountain peaks in the last half century without bursting =
into flames.

If you go still higher, temperatures rise naturally up to about 800 =
Kelvin in the Thermosphere. You run no risk of burning, though: the air =
density by then is so low that any heat gained from collision with air =
molecules cannot even offset the heat lost to outer space through =
radiation. The (accoustically generated) temperature spikes theorised in =
the article are therefore not so exceptional when viewed in context.

I suppose the Perlan people need to be well dressed, indeed, but not =
against the heat.

F.A.