on 10 may operation linebacker began with large-scale bombing operations against north vietnam by tactical fighter aircraft of the seventh air force and task force 77. their targets included the railroad switching yards at yên viên and the paul doumer bridge, on the northern outskirts of hanoi. a total of 414 sorties were flown on the first day of the operation, 120 by the air force and 294 by the navy, and they encountered the heaviest single day of air-to-air combat during the vietnam war, with 11 north vietnamese migs (four mig-21s and seven mig-17s) and two air force f-4s shot down. anti-aircraft artillery and over 100 surface-to-air missile firings also brought down two u.s. navy aircraft (one of which was flown by aces duke cunningham and william p. driscoll).