12/31/2007. Remarks by Johan Visschedijk: "This is the first prototype fitted with two 4,850 lb (2,200 KG) st Bristol Orpheus 1/5 turbojets, production aircraft were fitted with four 3,000 lb (1,361 kg) st Pratt & Whitney JT12A-6 turbojets. It was first flown on September 4, 1957."