The B-17's with the Triangle K tail markings are from the 379th Bomb Group (Heavy), 8th A.F.
The 379th BG consisted of the 524th, 525th, 526th & 527th Bomb Squadrons.
Stats on the 379th:
Combat OPS: May 43 - 45
Missions: 330
Sorties: 10,492
Payload dropped in tons: 26,460
MIA: 141
B-17 models flown: F & G models
to your Uncle.