sentences:  In 1934, Sir Alan Cobham founded Flight Refuelling Ltd (FRL) and by 1938 used a "looped-hose" system similar in design principle to that of the "Question Mark" to refuel large aircraft.In 1939 trials to perform aerial refueling of Short Empire flying boats began but were suspended after 16 flights following the outbreak of World War II.Near the end of the war, Avro Lincolns of RAF Tiger Force were to have been in-flight refueled by Avro Lancasters fitted with looped-hose systems for long range bombing operations against Japan but the capture of Okinawa obviated fielding of the tanker force.