[Trooper117]

Another point to consider is this.. A Squadron of Hurricanes for instance would not all be exactly the same.. They might be all the same Mark and brought up to the same spec, but there will be within that fleet of aircraft the 'flyers', that have an edge on top speed over the others..
There will be the Sqn 'nail'.. always seems to be slower than the others.
Then there is the 'problem child'.. always seems to be on the verge of overheating and requires more than the normal maintainance..
Couple that with the different levels of experience of the pilots flying them, and no two Hurri's will perform exactly the same......