Australia/NZ 1928 1st successful trans-Tasman crossing by "Southern Cross", Richmond aerodrome, Sydney to Wigram aerodrome Christchurch, NZ, 10-11 September 1928, crew Charles Kingsford Smith (pilot), Charles Ulm (co-pilot), Harry Litchfield (navigator), & Tom McWilliams (radio operator). Approx 15 covers are recorded (NZAMC No 31) but this is a new & quite unique discovery. AMSNZ expertised (2022). No official mail was carried on this pioneering flight but a very few covers were carried privately by the crew as souvenirs. According to both the Australian & New Zealand Air Mail Catalogues, these (mostly stampless) covers were, on arrival, taken to the Christchurch Chief Post Office by UIm, who was sworn in as a New Zealand postal officer. NZ 1d stamps were then added to the covers & cancelled with a Christchurch postal datestamp. This cover is quite different. It was carried personally by Tom McWilliams for his friend, H P Stephenson (the addressee on the cover). McWilliams at the time worked at the NZ Government Radio School in Wellington (& was "borrowed" for the flight), while Stephenson was a printer (& fellow radio enthusiast) in the same city. Unlike all the other known covers, this one bears an Australian 1d stamp cancelled by a "SPECIAL/SYDNEY" circular datestamp "11A. - 1 SE 28", plus a standard Australian "FORWARDED BY AIRMAIL" cachet (designed to enclose the datestamp impression). There is no NZ postal marking. The flight had originally been intended to depart on 2nd Sept but was postponed by 9 days due to unfavourable weather. The likely success of the flight was considered very marginal, even with favourable conditions. The only previous trans-Tasman attempts, by Moncrieff & Hood, in January 1928, had ended in disaster (the plane was lost without trace & has never been found). This cover was clearly taken to Sydney Chief Post Office on 1st September & cancelled there in anticipation of the intended flight the next day. It must then have been handed back to McWilliams to carry with him. It is the only cover recorded with both Australian postage stamp & postal cancellation prior to the flight's departure. On arrival in Christchurch, it was not taken by Ulm (together with the other souvenir covers) to the Chief Post Office to have a NZ stamp added and cancelled. Ulm may not even have been aware of the cover carried by McWilliams. This cover (with light vertical central fold) was discovered only recently and was previously unknown to the catalogue compilers. Offered with (a) accompanying contemporary envelope bearing explanatory text by H P Stephenson, and (b) copy of article by D Smitham. (Image)