With the fall of both Cambodia and South Vietnam in April 1975, the political climate between Washington and the government of PM Sanya had soured. Immediately after the news broke of the use of Thai bases to support the "Mayaguez" rescue, the Thai Government lodged a formal protest with the US and riots broke out outside the US Embassy in Bangkok. The Thai government wanted the US out of Thailand by the end of the year. The USAF implemented Palace Lightning, the plan to withdraw its aircraft and personnel from Thailand. The SAC units left in December 1975; and the 3rd Aerospace Rescue and Recovery Group left on 31 January 1976, however the base remained under US control until it was formally returned to the Thai government on 13 June 1976.