There is some history here than many may not know - but what a great article it is!
"Emphasizing the importance of the mission to the Philippines by way of Honolulu, no less a personage than Chief of the Army Air Forces General Henry “Hap” Arnold was there to see them off. Interrupting a quail hunting trip to address the crews, he warned them, “War is imminent. You may run into a war during your flight.” Armed with that admonition but nothing else, the big bombers began taking off at 10:30 pm. The prevalent feeling was that a war would not erupt until after they reached the Philippines. Therefore, none of the ships carried armor or ammunition; they were stripped down and packed to the brim with every gallon of fuel they could carry for the long hop from California to Hawaii. The B-17 Flying Fortresses did in fact carry their potent arsenal of .50-caliber machine guns, but they were boxed, stowed away, and packed in Cosmoline."