My dad was a bombardier with both the 3rd and the 90th Bomb Groups.  When Dad first went overseas in August of 1942, he was assigned to the 3rd Bomb Group.  At that time, the B-25's were considered a medium bomber and dropped bombs and used "skip bombing" tactics.  Dad talked about "skip bombing" during the Battle of the Bismarck Sea.  In April of 1943, their airfield was attacked by the Japs and all their B-25's were destroyed. Anyway, when the 3rd got their new planes, they came is refitted as low-level attack planes.  There was no room for a bombardier on those planes, so it was at that time that Dad was transferred to the 90th Bomb Group. 

So Dad served with the 3rd from August, 1942 until June of 1943.  He served with the 90th from June of 1943 until November of 1944.  Jack Heyn was the one who helped me figure this out when he came across my bumbling efforts on a message board as I was trying to do research on my Dad's military career.  I later found his original military documentation stuffed in the back of a closet at my Mom's house.  It was all housed neatly in a leather portfolio documenting his enlistment, pay stubs, transfers, letters of commendation, etc.

When he was with the 3rd Bomb Group, he was with the 13th Squadron (Grim Reapers). When he was with the 90th, he was with the 319th Squadron (Asterperious).  Attached is a photo of him and another of his bomber jacket. 

Linda Phillips

 Two aircraft of the 20th Combat Mapping Squadron - Artwork by Al Merkling