The first predecessor of the group was the 66th Aero Squadron,[note 1] which was organized in April 1918 at Kelly Field, Texas.

[2] Shortly after the end of the World War I, the squadron was demobilized and its personnel were absorbed by the Flying School Detachment at Eberts Field.

[1] The 20th Group's station at Nichols Field came under Japanese air attack as World War II began in the Pacific.

[6] By 24 December, all bombers had been flown to Australia and air force headquarters and all combat units except for a few fighters soon followed.

Colonel Harold H. George, of 5th Interceptor Command assumed control of all Air Corps units remaining in the Philippines.

With the flying mission being performed by a handful of fighter pilots, the bulk of the group's personnel were employed as infantry.