they were destroyed when Pyongyang was abandoned several days later. On 17 June 1951, at 01:30 hours, Suwon Air Base was bombed by two Po-2s. Each biplane dropped a pair of fragmentation bombs. One scored a hit on the 802nd Engineer Aviation Battalion's motor pool, damaging some equipment. Two bombs burst on the flightline of the 335th Fighter Interceptor Squadron. One F-86A Sabre (FU-334 / 49-1334) was struck on the wing and began burning. The fire took hold, gutting the aircraft. Prompt action by personnel who moved aircraft away from the burning Sabre prevented further loss. Eight other Sabres were damaged in the brief attack, four seriously. One F-86 pilot was among the wounded. The North Koreans subsequently credited Lt. La Woon Yung with this damaging attack. UN forces named the Po-2's nighttime appearance Bedcheck Charlie and had great difficulty in shooting it down – even though night fighters had radar as standard equipment in the 1950s. The wood-and-fabric material of the Po-2 had only a small radar cross-section, making it hard for an opposing fighter pilot to acquire their target. As Korean war U.S. veteran Leo Fournier remarked about "Bedcheck Charlie" in his memoirs: "... no one could get at him. He just flew too low and too slow." On 16 June 1953, a USMC AD-4 from VMC-1 piloted by Major George H. Linnemeier and CWO Vernon S. Kramer shot down a Po-2, the only documented Skyraider air victory of the war. The Po-2 is also the only biplane credited with a documented jet-kill, as one Lockheed F-94 Starfire was lost while slowing down to – below its stall speed – during an intercept in order to engage the low flying Po-2. Variants U-2: Basic model, built in large numbers as a two-seat primary trainer. It was also built in many different versions, both as civil and military aircraft. The U-2 variants also included a light transport, utility, reconnaissance and training aircraft. Power plant was the M-11 radial piston engine of 75 kW (100 hp). Later models were also equipped with uprated M-11 engines of 111 kW (150 hp). Some aircraft were fitted with a rear closed cabin, other were fitted with sledges or floats. U-2A: Two-seat agricultural crop dusting aircraft, powered by an 86 kW (115 hp) M-11K radial piston engine. Later redesignated Po-2A after 1944. U-2AO: Two-seat agricultural aircraft. U-2AP: Agricultural aircraft, with a rear cab replaced