The Lancastrian was basically a modified Lancaster bomber without armour or armament and with the gun turrets replaced by streamlined metal fairings, including a new nose section. The initial batch was converted directly from Lancasters; later batches were new builds.
In 1943, Canada's Victory Aircraft converted a Lancaster X bomber for civil transport duties with Trans-Canada Airlines (TCA). (After the war Victory Aircraft was purchased by what became Avro Canada). This conversion was a success resulting in eight additional Lancaster Xs being converted. The "specials" were powered by Packard-built Merlin 38 engines and featured a lengthened, streamlined nose and tail cone. Range was increased by two 400 gal (1,818 L) Lancaster long-range fuel tanks fitted as standard in the bomb bay. These Lancastrians were used by TCA on its Montreal–Prestwick route.
The modification of abundant military aircraft into desperately needed civil transports was common in the United Kingdom in the immediate postwar period: the Handley Page Halton was a similar conversion of the Halifax heavy bomber.
In 1945, deliveries commenced of 30 British-built Lancastrians for BOAC. On a demonstration flight on 23 April 1945, G-AGLF flew 13,500 mi (21,700 km) from England to Auckland, New Zealand in three days, 14 hours at an average speed of 220 mph (354 km/h).
The Lancastrian was fast, had a long range, and was capable of carrying a heavy load, but space inside was very limited as the Lancaster had been designed with space for its seven crew dispersed throughout the fuselage, and with the majority of the load being carried in the 33 ft (10.05 m) long bomb bay. Consequently, as passengers are bulky but low in weight, it was not suited to carry large numbers of passengers, but was suitable for mail and a small number of VIP passengers. BOAC used it for flights between England and Australia from 31 May 1945. It also served with the RAF; RAF Lancaster I serial number PD328, was converted to a Lancastrian and renamed Aries, as well as serving with QANTAS and Flota Aérea Mercante Argentina.