Stovall, Joel Clinton
Fleet Problem XXI ran from 1940-Apr-01 to 1940-May-17, again defending Hawaii from a sudden attack. Patrol Squadrons VP-21, VP-22, VP-23, VP-24, VP-25, and VP-26 began participation on 1940-Apr-09. Like their predecessors, PBYs proved vulnerable during attacks on surface ships, but they were valuable at tracking from high altitude. Although the fleet was ordered to remain in Hawaiian waters after the exercise (to send a message to Japan), deficiencies in communication and coordination between the Army and Navy air arms were not corrected in time for the attack on 1941-Dec-07.