This question courtesy of the movie Greyhound, in which air cover from either the American or British coasts seems to be a foolproof defense against U-boats. That being the case (was it the case?), having aircraft carriers accompany the convoys seems like a no-brainer. Did they do this? If so, I think I've never heard about it; if not, why not? Was air cover not all that effective against U-boats? Was the Pacific theater's demand for aircraft carriers so high that none could be spared for the Atlantic?