On June 19, 1968, Lassen, then a 26-year-old Lieutenant, junior grade flying a UH-2A "Seasprite" of HC-7 (assigned to the ), embarked on a mission to recover two downed Naval Aviators (from VF-33, off the ) whose F-4J plane had been shot down on a night interdiction mission deep inside North Vietnam. Upon reaching the hilly terrain where the aviators were hiding, Lassen made several attempts to recover the aviators, but dense tree cover, enemy weapons fire and intermittent illumination frustrated his efforts. Lassen turned on the landing lights of the helicopter, despite the danger of revealing his position to the enemy. After the pilots made their way to the helicopter and with his bullet-riddled helicopter dangerously low on fuel, Lassen evaded further antiaircraft fire before landing safely at sea on board the with only five minutes of fuel left in the helicopter's fuel lines. The account of the rescue was logged as a successful, routine search and rescue mission.