Where was the Sunderland's fourth assembly line?

Short answer

At White Cross Bay, on Lake Windermere: a new, albeit temporary, Shorts plant that turned out 35 aircraft. The programme's other three factories were Rochester and Belfast, both Shorts, and Dumbarton, run by Blackburn; the Sunderland III was built at all four.

Published: November 4, 2026 · Updated: November 4, 2026 · Edited by Above Ten Thousand · Editorial policy

Where was the Sunderland's fourth assembly line?

Short Sunderland Mk V Ex CC

A temporary plant on the shore of a lake

Of the Sunderland Mark III, most were built at Shorts' facilities in Rochester and Belfast, while another 35 came from a new, albeit temporary, Shorts plant at White Cross Bay, on Lake Windermere; a further 170 were manufactured by Blackburn Aircraft.

Split between the four factories

The Sunderland III was produced at the four factories involved in manufacturing the type: 186 examples at the Shorts plant in Rochester, 35 at Windermere, and the remainder at Belfast and Dumbarton.

The Mark III, the most numerous version

The Mark III proved to be the definitive Sunderland variant and was built in greater numbers than any other version of the aircraft. Its main change was a faired main step on the underside of the hull, which reduced hull-induced drag by ten percent, though it had some effect on the aircraft's behaviour on the water. One such Mk III, EJ134 of No. 461 Squadron RAAF, squadron code "N for Nuts", with eleven crew under F/Lt Colin Walker, was attacked by eight Junkers Ju 88C. On that 2 June 1943 the flying boat survived the attack, shot down three of the attackers, and came away riddled with holes and missing an engine. On several occasions the Sunderland was able to defend itself against several aircraft at once, and the Luftwaffe nicknamed it the "flying porcupine" for how heavily armed it was.