Before the Japanese attacked Pearl Harbor on December 7, 1941, the United States was desperate to know where the Japanese naval fleet was located and what they were up to. U.S. military intelligence knew that Japan was on the move and might attack some islands in the South Pacific, but did not consider an attack on Hawaii.
Just before the attack on Pearl Harbor, the U.S. was preparing special spy planes to begin reconnoissance missions in areas of the so-called “Mandates” — South Pacific island groups such as the Marshalls and Carolines that came under Japanese control after World War I.
However, the mission “never was.” On Sunday morning, December 7, 1941, the B-24 that was being prepared for the spy mission was sitting outside Hangar 15 at Hickam Field near Pearl Harbor with captain and crew nearby.
At about 8 a.m., bombs began falling on Hickam Field. Several of the crew were killed or wounded. The B-24 was destroyed, its would-be secret mission thwarted by world-changing events.
To learn more about the details of this planned mission and the corresponding events surrounding the bombing of Pearl Harbor, see this great summary story in the Washington Post: “The U.S. was looking for the enemy near Pearl Harbor — but it was looking in the wrong direction”
Also, a deep detailed history of these events was just released by National Archives senior archivist Greg Bradsher in a blog post: “Prologue to Pearl Harbor: The Spy Flight that Wasn’t”
Official letter regarding planned B-24 reconnaissance mission
source: National Archives and Records Administration