Cunliffe-Owen Aircraft Limited had a factory just a few hundred yards outside the eastern perimeter of Macmerry aerodrome, which they used for modification and repair work on Lockheed Hudsons. This was the first aircraft built in the United States which was used by the R.A.F. in the Second World War and was operated by Coastal Command for maritime reconnaissance and anti-submarine patrol work.

The firm had been formed in 1937 as a subsidiary of the British American Tobacco Company at Eastleigh, near Southampton, to build the Bumelli Flying Wing aircraft under contract, and was renamed Cunliffe-Owen Aircraft Limited in May 1938.

The work at Macmerry was carried out by a large number of employees, most of whom were women, bussed in to the site by S.M.T. from all over East Lothian and the surrounding area.