SOUTHWEST AFRICA → SOUTH AFRICA special flight cover from Windhoek to Kimberley via Marienthal, Keetmanshoop and Upington.  Flight was made to connect with Imperial Airways special Christmas London to Cape Town flight and marked the only occasion mail was conveyed from Windhoek to Cape Town by air until 1935.  Stamps cancelled by AIRMAIL WINDHOEK – KIMBERLEY LUGPOS special datestamp of 19 Feb 1931 on front and Kimberley20 Dec 1931 arrival datestamp at back.