Thank you for all these suggestions Gentlemen, the're going to keep me occupied for some while. In the meantime they have thrown up one not listed - The Flying North - by Jean Potter - it is based on a series of interviews carried out in the mid forties about the exploits of nine of the pioneer pilots in Alaska from around 1925 onwards, trying to establish trading routes before Panam appeared on the scene in the Forties.
Incredible stories - I found a copy through ABE Books or Amazon - can't remember which.
Cheers Entaxei
