The "Grapefruit Mission" was an attack on railroad marshalling yards in Köln, Germany on 28 May 1944.
The caption for the photo reads: "COLOGNE, GERMANY-Release line for U.S. 2,000 lb H.E. glide bombs is approximately 20 miles from target."
The aircraft at left appears to be 545th B-17G JD*Q 42-97573, while the one in the background is an unidentified B-17F.
Sourced from fold3.com