Are you talking about during the jump off from Normandy for the 2nd battle of France? They ended up dropping bombs on friendly troops.
From what I remember, they were bombing based on visual cues from the ground - smoke/roads/train tracks, and unlike in Normandy, where they came in perpendicular to the beach, and scared of dropping on the landing troops, their bombs hit up to several miles inland, completely missing the Atlantic Wall, they dropped parallel to allied lines, in a carpet area.
There is an account of this in Citizen Soldiers. I'll look it up when I go home to die of this damn uberflu.