During the actual aerial conflict, all RAF Spitfires were Spitfire Mk I and Mark II variants. However, only one Mk Ia and one Mk IIa (the latter with a Battle of Britain combat record) could be made airworthy, so the producers had to use seven other different marks, all of them built later in the war. To achieve commonality, the production made some modifications to "standardise" the Spitfires, including adding elliptical wingtips, period canopies and other changes. To classic aircraft fans, they became known as "Mark Haddies" (a play on Grp. Capt. Mahaddie's name).