During the 45-minute attack, the FEAF lost nearly half the planes at the base, and the remaining aircraft in the Philippines were captured by Japanese forces. This failure did not undergo any formal investigation, as troops were still shocked by the occurrences in Pearl Harbor. Major General Emmitt O’Donnell said it was not anyone’s fault, but the U.S. forces failed to assess the efficiency and speed of the Japanese Air Force.
The reality is that General Douglas MacArthur, commander in charge of the U.S. forces in the Philippines, should have placed American military forces in the Philippines on a proper war footing immediately following news of the Japanese attack on Pearl Harbor.
His failure to do so compromised the defense of the Philippines and resulted in the effective elimination of American air power in the western Pacific, forced the complete withdrawal of the United States Asiatic Fleet from Philippine waters, and paved the way for the successful Japanese invasion that followed. -- The American Spectator
Some blame General Brereton, but MacArthur was in overall command, and must bear much of the responsibility.
They were on high alert. US combat patrols were in the air at dawn but the Japanese attack never came due to bad weather on Formosa. By the time the weather on Formosa had cleared and the Japanese force took to the skies, the US fighters were out of gas and had to return to base for refueling and that is when the Japanese planes just happened to appear.
The gods of war just happened to favor the Japanese in Luzon on morning on Dec 8, 1941