What is "airmailing"

Usage examples of "airmailing".

They're airmailing the box home later today, probably, and the pathologist called it a heart attack.

They're airmailing the box home later today, proba­bly, and the pathologist called it a heart attack.

Martin, the noncom in charge, punched onto the teletype tape the intercepts that the post had picked up since airmailing in the bulk of the day's material, as well as the earlier ones.