Possible Clues:

• Churchill's 'so few': Abbr
• Spitfire fliers of WWII
• Armed service (inits)
• WWII British fliers
• 'Per ardua ad astra' org.
• The pilots of Penzance: Abbr.
• Org. with a college in Cranwell, England
• U.K.'s air arm
• Spitfire flyers, abbr.
• Berlin Airlift grp.