Thailand. ( Crash Mail ). 1947. Air Mail envelope addressed to Belgium bearing SG 296, 50s grey and orange and SG 307, 1b indigo ( pair ) tied by Bangkok date stamp with framed 'Retarde / par suite d' Accident / d' Aviation; on face.
The flying Boat "Portland" on the Dragon route from Hong Kong to Great Britain crashed into the sea when landing at Bahrain. A few different cachets are known. The 'Retarde' cachet being used on mail to France. This is the only cover known to Belgium.