Generally, aircraft Icons have grown a little bit ( the P-47's for example are larger than what used to be in the game )but in some cases, the wingspan and overall size has been slightly reduced to keep them in line with similar types but there has and will continue to be a difference in scale between fighters, twin-engined bombers and four-engine bombers but I am trying to keep a relative scale for each type. Those three types cannot be the same scale and fit into the game and there is no need for them to be the same scale as aircraft are only seen on map singly.
BUT that said your comment/question is hardly useful without examples.
I have found some older aircraft icons to be a bit too large but some a bit too small and in redoing them have made adjustments and these adjustments are NOT just "re-paints" they are totally redone from scale drawings.
The latest twin-engined bombers should be close to the same scale as should the single-engined fighters but twin-engined bombers and single-engined fighters
do not use the same scale and I have tried to come up with a formula but it all comes down to what was the wingspan of the last twin-engined bomber or single-engined fighter I built or rebuilt and is the new one the same or slightly smaller or slightly larger and then the wingspan for the new one is adjusted a bit one way or the other when I reduce the outline of the aircraft down from the scale drawing to create a template for the icon but there is no consistent scale across all aircraft types as there is generally with vehicles that have to co-exist in the map together.
An example of "scale" for single-engined aircraft
The wingspan of a 109 is less than a P-51. The P-51's in the game have a wingspan of 69 pixels the 109 is 59 pixels. I try to keep to odd numbers as a general concept as creating a balanced fuselage is easier when it's an odd number and since wings are in almost all cases the same the icons tend to be odd-numbered wingspans. There is a slight difference in ratio between the two....1.81 vs 1.86.
If the 109 was scaled to 1.86 like the P-51 it would average to 60.... 60 is an even number. If it was scaled to 61 it would a pixel too much but that's what the 109 on the right side is, in comparison, what it might be if the P-51 had been created to the same "formula" as the 109 it would be 67 wide instead of 69 but it's 69 and I can live with that as the difference shown here the one on the right is 67 and if you look real close you can see the difference...... you won't in the game and ultimately these things are built for the game and nothing else and in the game, they enter the map, make their attack and are gone and if the wingspan is 1 pixel less than "ideal" or two pixels "too much" it's nothing anyone PLAYING THE GAME is going to notice because only one aircraft can ever be on the game map at any one time and the only time real differences can be seen is when they are not in the game .