During August 1951, a second British-built Canberra (WD940) was flown to the US to act as a pattern aircraft for Martin, as well as to perform assorted trials and to support performance validation of airframe changes. On 21 December 1951, one of the British pattern aircraft (WD932) was lost in accident; although this was subsequently discovered to be caused by incorrect fuel scheduling having led to the tail-heavy aircraft exceeding its design limits during a maneuver, the crash jeopardized the entire program and invigorated the anti-Canberra political opposition. The crash did lead to some design changes in the face of political pressure, but these were not implemented on the first 75 aircraft to be produced.