The pack includes nine aircraft. The Gloster F.9/37, also known as the Gloster G.39, was a British twin-engined design from the Gloster Aircraft Company for a cannon-armed heavy fighter to serve with the Royal Air Force, planned before the Second World War. It was rejected in favour of the Westland Whirlwind, but it was a delight to fly. The project was resurrect when the Air Ministry launched the Specification F.18/40, for a specialist night fighter, with four 20 mm cannons at the nose and four Browning .303 mounted in a Boulton Paul turret. Gloster redesign the fuselage and used the F.9/37 wings fitted with two Rolls-Royce Merlin engines. The project included an Airborne Interception (AI) radar and was so promising that received support from the Air Staff who saw it as superior to the Bristol Beaufighter and the Air Ministry ordered one prototype that was not built. Someone at the Air Staff saw that the turret would compromised the performance and emitted a new Air Ministry Specification, the F.29/40, with eight .303 Browning machine guns installed in a tray bellow the fuselage firing ahead supplementing the four 20 mm Hispano Suiza cannons. The project, known unofficially as the Gloster Reaper, evolved to a one seat heavy fighter configuration and was dropped so that Gloster could concentrate on existing work and on the nascent British jet projects.