Demo P-51 and Spitfire Top Speed

[Marchochias]

Originally Posted by SleepTrgt

ive come close to 375 Mph level flight.

At what altitude? Was this with speed from a dive, or just gaining speed by going level?

I tried bringing the P-51 to 20 000 feet and diving, it reached 492 mph in the dive but the speed dropped off quickly after levelling.

The highest I could reach at very low altitude was 280 mph.

Does anyone know if the speed indicator is showing true airspeed or indicated airspeed?