On 12 October 1937, the maiden flight took place of the first production Hurricane I, which was powered by a Merlin II engine and flown by Flight Lieutenant Philip Lucas. Production deliveries had been delayed by roughly six months due to a decision to equip the Hurricane only with the improved Merlin II engine, while the earlier Merlin I had been prioritised for the Fairey Battle and the Hawker Henley. By the following December, the first four aircraft to enter service with the RAF had joined No. 111 Squadron, stationed at RAF Northolt. By February 1938, No. 111 Squadron had received 16 Hurricanes. Upon the outbreak of the Second World War, over 550 Hurricanes had been produced, which had equipped a total of 18 squadrons, while a further 3,500 aircraft were on order.