Merchant aircraft carrier

A merchant aircraft carrier (also known as a MAC ship, the Admiralty's official 'short name') was a limited-purpose aircraft carrier operated under British and Dutch civilian registry during World War II. MAC ships were adapted by adding a flight deck to a bulk grain ship or oil tanker enabling it to operate anti-submarine aircraft in support of Allied convoys during the Battle of the Atlantic. Despite their quasi-military function, MAC ships retained their mercantile status, continued to carry cargo and operated under civilian command.

Source: Wikipedia — Merchant aircraft carrier (CC BY-SA 4.0)