In April 1961, an advance party of the 6010th Tactical Group, USAF, arrived at Don Muang at the request of the Royal Thai government to establish an aircraft warning system. On 20 April 1961 six F-100 Super Sabres from the 510th Tactical Fighter Squadron based at Clark Air Base deployed to Don Muang in Operation "Bell Tone". In March 1962, a small detachment of F-102 Delta Daggers from the 509th Fighter-Interceptor Squadron, from Clark AB, Philippines were sent to Don Muang. Their mission was to bolster the air defense capabilities of the Royal Thai Air Force. For the next several years, a minimum of four F-102 interceptors were kept on alert at Don Muang.