Gestation
The idea of simple adaptations of bulk cargo ships for aircraft had been considered by the Admiralty for some time. It would provide desperately needed air cover for convoys without losing valuable cargo capacity. There was, however, resistance to the concept arising from several technical issues; the 12 knot speed was considered too slow for aircraft operation, the design and development time was expected to take too long and aircraft movements on steel decks over highly flammable fuel cargoes was considered too dangerous.
The then Director of Merchant Shipbuilding, Sir James Lithgow, made a rough design on the back of an envelope and offered to adapt two ships about to be built at his family's shipyard. This was on condition that "I am not interfered with by the Admiralty". Work started in June 1942 on two grain carriers, Empire MacAlpine and Empire MacAndrew. Ten more were ordered by October and a total of thirty-two were planned (cut back to nineteen with the delivery of escort carriers).
Read more about this topic: Merchant Aircraft Carrier