- After being alerted of the Japanese attack on Hawaii, the B-17s of the 19th Bombardment Group at Clark Field were ordered into the air on the morning of 8 December while FEAF commander Maj. Gen. Lewis H. Brereton sought approval to attack Japanese airfields on Formosa in accordance with pre-war war plans. After two hours, Brereton received approval to carry out a late afternoon strike and recalled the B-17s to Clark to refuel and load bombs. P-40s on patrol over Luzon ran short of fuel and also landed shortly before noon local time. Of the 19 bombers based at Clark, one was in the air on a reconnaissance flight and another took off to flight test a newly-repaired generator. A 20th B-17 was nearing Clark, having been sent up from Mindanao to repair a wing fuel tank. Three squadrons of P-40s took off just before noon to continue patrols but none were assigned the area of Clark Field. Radar and observers detected a large force of Japanese aircraft, delayed several hours on their bombing mission by fog over their bases, but poor communications and other errors failed to alert Clark of their approach. 108 Japanese naval bombers in two formations struck the field shortly after 12:30, destroying all but four P-40s on the field preparing to take off, and causing immense destruction to facilities. A wave of 80 Mitsubishi A6M Zero fighters arrived shortly after, and unopposed, strafed the base for 45 minutes, destroying all but five of 17 B-17s caught on the ground, and damaging three of the others so that they did not fly again. Within a week, only 14 of the original 35 based in the Philippines remained operational, stationed at Del Monte Airfield on Mindanao, attempting to remain out of range of Japanese air attacks. Beginning on 17 December, the surviving B-17s, badly in need of maintenance, began evacuate to Batchelor Field near Darwin, Australia.
- The 27th Bombardment Group, less one squadron, arrived at Fort William McKinley by ship on 20 November; however all of its A-24 aircraft had not yet arrived by 6 December. To avoid capture or destruction, the ship carrying the crated planes was diverted to Australia when the Japanese isolated the Philippines. The personnel of the 27th were formed into the "2nd Provisional Infantry Regiment" on Bataan. The 27th Bomb Group became the only Air Force unit in history to fight as an infantry regiment, and were the only unit to be taken captive in whole. After surrendering, they were forced to endure the infamous Bataan Death March. Of the 880 or so Airmen who were taken, less than half survived captivity. The air echelon of the 27th Bomb Group eventually reformed in Australia in 1942 and fought in the Dutch East Indies and New Guinea campaigns.
- The 24th Pursuit Group flew its last interception on 10 December and made several small-scale attacks on Japanese landing forces, but ceased to exist as an operational air combat organization by 24 December 1941. Its personnel were also sent into Bataan as the "1st Provisional Infantry Regiment" as a reserve force to the Philippine Division. Although destroyed as a unit, the group remained on the list of active AAF units until the end of the war.
- The P-26s of the Philippine Army Air Corps' 6th Pursuit Squadron were mostly destroyed on the ground in the first Japanese attacks following Pearl Harbor, but two flown by Filipino pilots scored victories over Japanese airplanes. In 1942, in a desperate defense of their homeland, the few surviving P-26s which the Filipino 6th Pursuit Squadron still had at its disposal were completely overwhelmed by Japanese A6M Zero fighters.
- The 34th Pursuit Squadron, attached to the 24th Pursuit Group, received 35 Seversky P-35As when its P-40s failed to arrive before war broke out. On 8 December 1941, when the Japanese launched the first air attacks on the Philippines, the obsolescent fighters proved completely inadequate for the task of air defense, too lightly armed and lacking both cockpit armor and self-sealing fuel tanks. Most were shot down in combat or destroyed on the ground in the first days of combat. By 12 December there were only eight airworthy P-35As remained.
Establishment of Fifth Air Force
The 7th Bombardment Group was withdrawn to India in March 1942, leaving the 19th to carry on as the only B-17 Fortress-equipped group in the South Pacific. About this time it was decided that replacement B-17s would not be sent to the southwest Pacific, but be sent exclusively to the Eighth Air Force which was building up in England. By May, Fifth Air Force's surviving personnel and aircraft were detached to other commands and the headquarters remained unmanned for several months, but elements played a small part in the Battle of the Coral Sea (7–8 May 1942) when the 435th Bomb Squadron of the 19th Bomb Group saw the Japanese fleet gathering in Rabaul area nearly two weeks before the battle actually took place. Because of the reconnaissance activity of the 435th Bomb Squadron, the US Navy was prepared to cope adequately with the situation. The squadron was commended by the US Navy for its valuable assistance not only for its excellent reconnaissance work but for the part played in the battle.
Headquarters Fifth Air Force was re-staffed at Brisbane, Australia on 18 September 1942 and placed under the command of Major General George Kenney. United States Army Air Forces units in Australia, including Fifth Air Force, were eventually reinforced and re-organised following their initial defeats in the Philippines and the East Indies. At the time that Kenney had arrived, Fifth Air Force was equipped with three fighter groups and 5 bombardment groups.
In addition, Fifth Air Force controlled two transport squadrons and one photographic squadron comprising 1,602 officers and 18,116 men.
Kenney was later appointed commander of Allied air forces in the South West Pacific Area, reporting directly to General Douglas MacArthur. Under Kenney's leadership, the Fifth Air Force and Royal Australian Air Force provided the aerial spearhead for MacArthur's island hopping campaign.