Here's a summary that matches your description:
* Two American pilots, flying a bomber mission, are lost and crash-land in the countryside.
* One of the pilots falls for a local girl, living on a farm.
* They discover a strange, eerie presence on the farm, which turns out to be the ghost of a German pilot who crashed there during the war.
* A German plane bombs the barn, seemingly confirming the ghost's story.
The film features a combination of romance, mystery, and war-time intrigue, fitting your description.