Complex sentence: In the movie, Daniel mentions having flown a B-25 Mitchell (which he pilots later on in the movie) even though the B-25's maiden flight was in August 1940,10 months after Daniel had already been frozen.
Split into simpler sentences: In the movie, Daniel mentions having flown a B-25 Mitchell (which he pilots later on in the movie). The B-25's maiden flight however was in August 1940,10 months after Daniel had already been frozen.