 In order to at least partially improve the view from the Mustang, the British had field-modified some Mustangs with clear, sliding canopies called Malcolm hoods (designed by Robert Malcolm), and whose design had also been adopted by the U.S. Navy's own F4U-1D version of the Corsair in April 1944.The new structure was a frameless plexiglas moulding which ballooned outwards at the top and sides, increasing the headroom and allowing increased visibility to the sides and rear.Because the new structure slid backward on runners, it could be slid open in flight.