National Geographic : 1926 Jan
ON THE TRAII, OF THE AIR MAIL Photograph Courtesy U. S. Post Office D)epartment TAKING ON GASOLINE AT AN EMERGENCY FIELD Photograph by Captain A. W. Stevens MECHANICS CHECKING OVER TIE ENGINE The success of an air line depends largely upon the care and thoroughness of work done on the ground before each flight begins. Every plane is carefully checked over before and after each trip. Note one of the landing lights on the tip of the upper wing. Metal propellers, as seen here, are rapidly replacing the former metal-tipped wooden propellers.