Highland Airways
Highland Airways was awarded a contract by the Post Office to carry mail on their service between Inverness and Kirkwall, and an experimental service began on 29th May 1934 with a flight by a de Havilland Dragon piloted by Capt. E.E. Fresson. Wick was added to the airmail service from 1st December, and from 10th December mail was transferred between Thurso and Wick by rail or bus. On 25 March 1935 mail from Lerwick in the Shetland Isles was carried by ship to Kirkwall and flown to Inverness for transfer by rail to Glasgow for distribution.

Highland Airways issued vignettes for the first mail flight between Inverness and Kirkwall, which was sold for 2/-, and for the Wick service, which was sold for 1/-.
29th May 1934.
Imperforate. Number printed: 1,250.
Aircraft and map of route.

1st December 1934.
Perf: 11. Number printed: about 1,000.
Map of route.

Highland Airways Air Mail Magazine Volume 1, pp. 54-55, A. Phillips (1939)
Highland Airways Air Mail Magazine Volume 1, pp. 114-115, A. Phillips (1939)
Official British Inland Airmails Part 2. John C.W. Field, British Philatelic Bulletin, Volume 24 Number 6, February 1987