This part of the series was set in the late 1944 early 1945 time frame. By this time in the war the Germans were no longer able to operate their U-boats in wolfpacks against allied shipping.
The Navy, as well as the Royal Air Force's Coastal Command had Anti-Submarine Warfare versions of the B-24 bomber operating out of Britain and would have been the logical choice for flying the missions depicted in support of the Navy's surface forces.
The only U.S. carrier sunk by a German U-boat was the USS Block Island, CVE-21, in May of 1944, long before the time period of this episode.
Major Stovall was never grounded in Season 2 due to poor eyesight. In Season 2's Storm at Twilight (1965), there are questions about his eyesight and he nearly grounds himself, but eventually returns to combat as Colonel Gallagher's co-pilot and brings the aircraft home when Gallagher is wounded, after which Gallagher tells Stovall, "Harvey, when this is all over, you can fly me home!"
The opening establishing shot of Bomber Command is of a 3 story brick building. Unfortunately there is a large shadow on the roof of a gigantic palm tree, revealing that the location is not England (where palms do not grow) but Southern California .
The map of the target area shows the Straits of Gibraltar, the opening to the Mediterranean Sea. This area would have been far out of range for 8th Air Force bombers, and as the Germans were no longer in France or North Africa, it would have been impossible for them to have had fighter coverage for their submarine wolfpack.