Aerial refueling craft was eventually modified by Airspeed to Cobham's specification, for a non-stop flight from London to India, using in-flight refueling to extend the plane's flight duration. Meanwhile, in 1929, a group of U.S. Army Air Corps fliers, led by then Major Carl Spaatz, set an endurance record of over 150 hours with the "Question Mark" over Los Angeles. Between June 11 and July 4, 1930, the brothers John, Kenneth, Albert, and Walter Hunter set a new record of 553 hours 40 minutes over Chicago using two Stinson SM-1 Detroiters as refueler and receiver. Aerial refueling remained a very dangerous process
Harlan Gurney had attended the US Army Air Corps flight school at Brooks Field with Lindbergh. In 1927, when Lindbergh took leave from Robertson Aircraft to make his epic non-stop New York to Paris flight, Gurney replaced him as Robertson’s chief air mail pilot and flight instructor. Robertson was soon absorbed by Universal Air Lines for which Gurney became director of operations. In 1929 he was lured to Transcontinental Air Transport (TAT) for which Lindbergh was technical advisor. TAT, which was known as 'The Lindbergh Line,' offered coast to coast transportation in 36 to 48 hours hours using a combination of linked