 Further air cover was provided by the introduction of merchant aircraft carriers (MAC ships), and later the growing numbers of American-built escort carriers.Primarily flying Grumman F4F Wildcats and Grumman TBF Avengers, they sailed with the convoys and provided much-needed air cover and patrols all the way across the Atlantic.Larger numbers of escorts became available, both as a result of American building programmes and the release of escorts committed to the North African landings during November and December 1942.