Because of their high profile and degree of threat, the PACVs and ACVs in Vietnam became major targets. The Viet Cong used ambushes and naval mines against the PACVs. Mines proved especially effective: Army ACV 902 was destroyed by a tripwire-triggered mine on 9 January 1970. Though no one onboard was killed, 14 men were injured and the attack slowed the pace of ACV operations because of Army regulations stipulating that the hovercraft work in pairs to protect each other. When ACV 901 was destroyed by a command-detonated mine on 3 August 1970, killing three, the ACVs were deactivated. The 39th ACV Platoon ceased operations on 31 August 1970 and officially left Vietnam in September, transferring their sole surviving ACV to the Army Transportation Museum in Virginia. Navy PACVs returned to the continental United States that August as well. In total, Navy PACVs saw more than 4,500 hours of operation.