Short Empire S.23 Mk III Atlantic

The Short Empire was designed for Imperial Airways' routes to South Africa and Australia, where no leg was much over 500 miles. Once the design was finalised and production had begun, it was recognised that — with some American pressure — a transatlantic service would also be desirable. The S.23's range was less than that of its American counterpart, the Sikorsky S-42, and was not enough for a genuine Atlantic service.

Two boats, Caledonia and Cambria, were lightened and fitted with long-range tanks; both were also used in experimental in-flight refuelling trials so they could make the crossing. The modifications cost passenger and cargo capacity.

On 5 July 1937 the first Atlantic crossing by an Empire flying boat took place: Caledonia, piloted by Captain W. N. Cummings, flew the 3,207 km from Foynes, Ireland, to Botwood, Newfoundland. The same day an American Sikorsky S-42 flew the opposite direction. Caledonia took just over fifteen hours, flying between 460 and 1,520 m, at an average of about 210 km/h; on the return flight, on 22 July 1937, it covered the same route in twelve hours, faster than the S-42. In August 1937 Cambria completed the west-east crossing in fourteen hours twenty-four minutes.

In 1937 Cavalier was shipped to Bermuda and, after reassembly, opened the service between the islands and New York City on 25 May 1937. That route explains the existence of the S.23's other sub-mark, the Mk II Bermuda, also of two aircraft.