 In 1966 , the Army awarded Lockheed a contract for ten AH @-@ 56 prototypes , but as a stopgap also ordered the simpler AH @-@ 1G Cobra as an interim attack aircraft for combat in Vietnam . The AH @-@ 56 's maiden flight took place on 21 September 1967 . In January 1968 , the Army awarded Lockheed a production contract , based on flight testing progress . A fatal crash and technical problems affecting performance put Cheyenne development behind schedule , resulting in the cancellation of the production contract on 19 May 1969 . Development of the Cheyenne continued in the hope that the helicopter would eventually enter service . 
