In March 1944 Cunningham relinquished command of 85 Squadron. He was appointed group captain in command of Night Operations at No. 11 Group RAF. At 26 he was one of the youngest to hold that rank. Air Marshal Roderick Hill asked him to report to de Havilland in company with Adolph Malan. They were to test-fly the de Havilland Vampire. Cunningham commented that the machine would make an ideal night fighter. Although he was not familiar with the workings of the de Havilland Goblin turbojet, he recommended that if the cockpit was extended to allow for a navigator and the fuel tanks were enlarged, the type could make a formidable interceptor. While test-flying, Cunningham and Rawnsley carried out a sortie over Normandy from RAF Uxbridge. They overflew the British sector on the 9 June 1944 as the Battle for Caen began. They were vectored onto enemy aircraft but were unable to hold their contacts.