Complex sentence: "F-Freddie" was out of commission for three weeks, but once repaired Pickard took her on a mission to attack Cleve, and again was riddled with flak, putting her back in the hanger for repairs.
Split into simpler sentences: F-Freddie was out of commission for three weeks. Again "F-Freddie" came back riddled with flak, putting her back in the hanger for repairs.