One of the integral parts of the Igloo White surveillance system was the little QU-22, a unique aircraft in Southeast Asia in that it could be flown either with or without a pilot.  The QU-22 was a highly modified version of the Beech A36 Bonanza light aircraft under the Pave Eagle II programme.  Although the aircraft could be operated by remote control as a pilotless drone, it was usually flown with a pilot on board in Southeast Asia.  The aircraft was fitted with wingtip fuel tanks and a Continental IO-520-B engine with a special reduction gearbox to turn the propeller at a very low rpm to reduce the aircraft’s noise signature.  The aircraft was also fitted with avionics equipment that received the information transmitted by the acoustic and seismic sensors that littered the Ho Chi Minh Trail.  The information was retransmitted either to an orbiting EC-121R or direct to the Eagle White facility at Nakhon Phanom for analysis.  A total of six YQU-22As and 27 QU-22Bs were produced and the first aircraft arrived at Nakhon Phanom in March 1969.  Nine of the aircraft were lost during the war.  Many of the survivors were later converted back to a more standard configuration and sold to private owners in the USA.