ETE4130348: Philadelphia Arsenal (Pennsylvania) USA 1930: Colonel Charles Lindbergh (1902-1974) inspects the TAT (Transcontinental Air Transport) line on board the Ford “City of Columbus”. From left to right; Lieutenant Commodore W.W Webster, Charles Lindbergh, David M. Schaeffer and John Collins (Chief Pilot) / Bridgeman Images
ETE4129282: New York City (USA), circa 1930: Professor Ernst Frederick Werner Alexanderson (1878-1975) (left) and his assistant S.P Nixdorff examining the light altimetre echo or colours indicate altitude of flight - New York City (USA), ca 1930: Inventor Ernst Frederick Werner Alexanderson (1878-1975) (left) and his assistant S.P Nixdorff with his new radio echo altimeter where colored lights indicate altitude / Bridgeman Images