The last of the original six Transport Plane issues and the highest value in the series was the 50-cent stamp, printed in the color gold orange. It was issued on October 29, 1941. The primary purpose of the stamp was to pay the fifty-cents-per-half-ounce transpacific airmail rate to the Philippine Islands. It also found usage for partial payment with other stamps to pay some higher international airmail rates then in effect. Solo (single stamp) usages were occasionally possible by paying for combinations of lower airmail rates along with registry or Special Delivery service.
While the stamp's primary intended use was for airmail to the Philippine Islands, airmail service over the Pacific Ocean was interrupted only five weeks later. Beginning December 7, 1941, the date of the Pearl Harbor, Hawaii, bombing by the Empire of Japan, the transpacific routes were closed beyond Hawaii for almost four years, not resuming until late in 1945. Most airmail letters mailed after November 15 enroute to the Far East were returned to the senders and marked as "service suspended."