Due to its thick, short wing it was able to out-turn the main German night fighters, the Messerschmitt Bf 110 and the Junkers Ju 88. Heavy bombers still needed defensive armament for protection, even at night. The Stirling's low operational ceiling of just 12,000 ft (3,700 m) — also caused by the thick wing — meant that it was usually picked on by night fighters; within five months, 67 of the 84 aircraft in service had been lost.