Il miglior squadrone di piloti britannici della seconda guerra mondiale era composto da europei orientali, principalmente polacchi (Squadrone 303)

Not quite, they were the best squadron during the Battle of Britain(July – October 1940). Not the entirety of WW2. Many of the great English pilots where either dead, Injured, shot down and captured etc. by that time.

>As the Battle of Britain wore on, and the shortage of trained pilots became critical, the exiles were accepted into RAF squadrons and two Polish fighter units, Nos. 302 and 303 Squadrons, During the Battle of Britain the Czech Sergeant Josef Frantisek was Fighter Command’s most successful pilotwere formed. Once committed to action, the Poles flew and fought superbly, shooting down 203 enemy aircraft for the loss of 29 pilots killed.

>No. 303 Squadron became the most successful Fighter Command unit in the Battle, shooting down 126 German machines in only 42 days. With 17 confirmed victories, Sergeant Josef Frantisek, a Czech national serving with No. 303 Squadron, was one of Fighter Command’s most successful pilots.

https://www.rafmuseum.org.uk/research/online-exhibitions/the-polish-air-force-in-world-war-2/303-squadron/#:~:text=No.,Fighter%20Command’s%20most%20successful%20pilots.

I think you mean “composed”. Or alternatively you mean “comprised”. But in that case the most correct usage would be “Eastern Europeans, primarily Polish comprised the best British pilot squadron (Squadron 303)”

Come on dude, we’re not eastern Europeans, Poland is located in C E N T R A L Europe. Also, the 303rd was entirely Polish with the exception of one Czech pilot.