The actual sortie strength and its range problem

A torpedo occupied the position that could otherwise carry a centreline long-range fuel tank, so Swordfish crews used a 60-imperial-gallon auxiliary tank in the rear cockpit. Illustrious had twenty-four Swordfish assigned, but tainted petrol reduced the launchable force to twenty-one. Twelve aircraft formed the first wave and nine the second, although engine trouble forced one of the latter to turn back, leaving twenty to reach Taranto; ten carried torpedoes. The account also notes Malta-based Maryland reconnaissance and a Sunderland flight as part of the wider preparation for the night attack.