During 1943, the chief designers of Saunders-Roe and Short had collaborated to produce a preliminary design specification for an innovative large flying boat. This design specification defined various criteria for the proposed aircraft, which would be the largest all-metal flying boat ever built; performance criteria included a weight of 140 tons, a pressurised 'double-bubble' hull, a 214-foot wingspan, a height of 55 feet 9 inches, and a length of 148 feet. The proposed aircraft would be capable of a cruising speed of 340 MPH at an altitude of 37,000 feet, a range (dependent on payload) of 5,190–3,640 miles, and be outfitted with luxurious accommodation for a total of 104 passengers.