Errr...
TP,
In theory it's possible for an A340 or 747 to exceed Mach 1... however the temp would have to change a heckuva lot and you'd have to be cruisin' at a very high Mach number. I know that a 747 has exceeded Mach 1.3 in a spin recovery dive, but there's NO WAY the Airbus would let you do it. It's hardwired to keep you from doing things that you shouldn't! Unless you're in DIRECT mode of course! :P
Nial