By-KLM-Dutch-Airmail
Mark: Because of faster possibility Airmail via Railway
Air France - Louis Bleriot
Air balloon - Gordon Bennet - Belgium - Poland - Soviet ...
Air balloon - Gordon Bennet - Belgium - Poland
Air balloon flight - St. Ingbert Saar - Luxembourg
Helicopter mail
Air balloon - Balloon mail
40 Yeaqrs KLM - Royal Dutch Airline