by mid-month, nearly all of north vietnam had been cleared for bombing raids for the first time in over three years. air force and navy commanders and pilots were relieved that nixon (unlike president johnson) left the operational planning to local commanders and loosened the targeting restrictions that had hampered operation rolling thunder. between 1 may and 30 june b-52s, fighter-bombers, and gunships had flown 18,000 sorties against formidable anti-aircraft defenses with the loss of 29 aircraft.