The Book of Radio, Charles William Taussig, 1922, pages 202-203:

    One of the most striking examples of the value of having amateur radio stations scattered all over the country is illustrated in the following story:
    The U. S. Mail Plane was delayed in Cleveland. The authorities would not let it leave the ground, owing to a break in the radio equipment which was being repaired. The impatient pilot, anxious to start, condemned the radio as being of no service to him in flights and requested that he be permitted to start without it. He was not allowed to do this, however, for the regulations are very strict in regard to mail airplanes. After further delay, the radio was fixed, and the plane left on its long flight to Chicago. The trip was uneventful, until the plane neared Chicago, where a heavy ground fog obscured both land and lake. Blind for all practical purposes, the aviator circled around and around, seeking the landing place. Through a slight rift in the fog bank below him, he caught a glimpse of Lake Michigan. This was not very reassuring and he was at a loss to know just where the landing field lay. After more circling about, their gas became almost exhausted, and in desperation he finally told his radio operator to send out a Q S T (general call) and ask any radio station who heard them to call the Mayfair landing field on the telephone and ask them to send up rockets. In an incredibly short time, rockets were seen piercing the fog bank below, and a safe landing was made. Upon inquiry, the pilot learned that six different amateurs had telephoned their message to the landing field.