What piston engine aircraft do you think was the pinnacle of achievement during the war?
The aircraft has to have been developed during the manufacturing country's tenure as a combatant.
The aircraft has to have flown during the manufacturing country's tenure as a combatant. It doesn't matter if the aircraft saw actual combat or even became operational.
Prototypes and experimental / developmental aircraft count as long as they were flying during the manufacturing country's tenure as a combatant.
The aircraft has to have been developed during the manufacturing country's tenure as a combatant.
The aircraft has to have flown during the manufacturing country's tenure as a combatant. It doesn't matter if the aircraft saw actual combat or even became operational.
Prototypes and experimental / developmental aircraft count as long as they were flying during the manufacturing country's tenure as a combatant.