> Of John S. Ward >It's simply wrong to call it "feet" To be pedantic, they don't actually call it 'feet'. They call it 'flight level' (e.g. flight level 330'). But hectofeet is implied. It is often called 'pressure altitude', which is a clue to what is being calculated.
Note that pressure goes down as height goes up. So if we used hPa, an aircraft could take off from an airport at 1013 and climb to 262. It is also non-linear, so either the separation distances would increase with altitude, or the hPa values would be further apart.
