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
The Airplane Factory Sling 4 The Airplane Factory Sling 4 The Sling 4 is a development of the Sling 2 to accommodate four people, built by The Airplane Factory of Johannesburg, South Africa. The Sling 4 is an all-metal, low-wing, fixed tricycle gear homebuilt aircraft. The aircraft was developed in 2009. The canopy was modified to include gull-wing doors. The aircraft features flaps with 40 degrees of travel. In July 2013 a Sling 4 was flown by Mike Blyth and his son from South Africa to AirVenture in Oshkosh, Wisconsin, United States. The flight included a 14-hour over-water leg. The aircraft carried 20 hours endurance