Not quite. It was thought to be a flight of six B-17s incoming from San Francisco. The US Army was increasing its B-17 force at the time in the expectation of hostilities in the Pacific. The B-17s actually did show up in the middle of the attack.

http://www.dispatch.com/content/stories/national_world/2010/02/25/officer-who-ignored-pearl-harbor-warning-dies.html

http://articles.baltimoresun.com/1991-11-29/news/1991333114_1_lockard-attack-on-pearl-harbor-attack