In the early to mid-20th century, airmail networks were inconsistent and expensive. A sender might pay the airmail surcharge for a trans-oceanic flight but not for the subsequent rail or sea transport in the destination continent. The Directive:
The term "Jusqu-à" is French for or "up to" . In postal history, these markings served a critical operational function: they indicated the specific point where airmail transmission ended and surface transport (train or ship) began. They were typically applied when: Jusqu-a Airmail Markings- A Study Ian McQueen