The 30-cent value was the fifth in the new Transport Plane Series. Printed in blue, this stamp was issued almost a month after the 20-cent stamp. Ceremonies were held in Kansas City, Missouri, on September 25, 1941. The stamp's primary purpose was to pay the thirty-cents-per-half-ounce international airmail rate to Europe. The airmail route was over the Atlantic Ocean from the east coast of the U.S. via FAM (Foreign Airmail Route) 18, which had been inaugurated on May 20, 1939. This was the main or southern air route via Horta, Azores, and Lisbon, Portugal. Approximately a month later, on June 24, 1939, a second or northern route of FAM 18 was inaugurated from Canada via Newfoundland and Foynes, Ireland to Southampton, England.
Only seven weeks after the 30-cent transport stamp was issued, following the entry of the U.S. into WW II on Dec. 8, 1941, U.S. airmail service was suspended to most of the countries in Europe that were occupied or controlled by Germany. Even airmail sent in late November 1941 and which was already in the mail stream was returned and is usually found with "service suspended" and "return to sender" markings.