Complex sentence: With two drop tanks, these P-38Fs were flown across the Atlantic with a B-17 Flying Fortress as navigator in early 1942, making the P-38 the first USAAF fighter to reach Britain.
Split into simpler sentences: With two drop tanks, these P-38Fs were flown across the Atlantic with a B-17 Flying Fortress as navigator in early 1942. So the P-38 was the first USAAF fighter to reach Britain.