 Although these extra fee stamps were issued for use on mails to be serviced by air, the legend "AIR MAIL" did not appear on any USPOD stamp until eight years later when the 10-cent C-7 rectangular was issued on February 13, 1926, two days before the first ever mail flight under contract with a commercial carrier was made on February 15, an eastbound trip between Detroit and Cleveland over CAM Route 7.Angered by the insistence of Second Assistant United States Postmaster General Otto Praeger that they fly their routes on time even in zero visibility conditions in order to maintain fixed schedules or be fired – a policy that had resulted in 15 crashes and two fatalities in the previous two weeks alone – U.S. Airmail Service pilots began a spontaneous strike on July 22, 1919.After Preager and the United States Post Office Department received much negative comment in the press, the strike ended in less than a week, on July 26, 1919, when the Post Office Department agreed that officials in Washington, D.C., would no longer insist on pilots flying in dangerous weather conditions.