A catapult-armed merchant ship added one fighter to a convoy's defenses. That fighter could attack a maritime patrol aircraft whose loss mattered because relatively few were available. The fighter itself was expendable: its pilot had to abandon it and be picked up afterward. This offered a practical response to a limited aerial threat without requiring the convoy to have a carrier.
Notable Point · 1:56:48-1:57:22
A CAM ship traded one fighter for a maritime patrol aircraft
A catapult-armed merchant ship could launch a single fighter against a scarce enemy patrol aircraft, then recover the pilot after the fighter was abandoned.