from what I have seen they were both doing about what they should have been.
The threat of sabotage was very reasonable and there was in fact an active Japanese spy organization on the island.
Also McArthur got a bad rep in the Philippines for having his planes on the ground. He was going to great lengths to protect the planes and was expecting an attack. He had established outposts to report any Japanese planes. He was keeping as many as possible in the air.
Luck just was against them. They got a single report of Japanese planes and tried desperately to confirm it but were unable to do so. The outposts had just been formed and were giving a lot of false reports. The planes were low on fuel and they finally had to bring them down, just as the Japs attacked it turned out.