http://www.airspacemag.com/issues/20...er/rooftop.php

In the USA

By 1941, some 13,000 marks had been painted on barns, hangars, skyscrapers, oil tanks, and train stations. Now, in January 1942, on the heels of the attack on Pearl Harbor, the Civil Aeronautics Administration, goaded by the War Department, directed that all air markers near both coasts be obliterated.

“The number of military ships which have been forced to land due to running out of gasoline…has been appalling,” Noyes later wrote to her bosses, blaming the loss of air markers. The CAA chief of airways countered: “The Army feels that the value of markers to the enemy overshadows the need by our pilots; therefore the air marking project will remain suspended for the duration of the emergency.”

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