Complex sentence: No aircraft are lost; 70 B-17s and 58 P-51s land in the UK, five B-17s and six P-51s, either left in Italy or returning there during this mission also return to the UK, completing FRANTIC-5.
Split into simpler sentences: No aircraft are lost; 70 B-17s and 58 P-51s land in the UK. Five B-17s and six P-51s, either left in Italy or in the process of returning there during this mission also fly to the UK, completing FRANTIC-5.