There is great confusion around the history of the first LeO 455s. The re-engineered prototype with 14 R-0/1 flew for the first time at Villacoublay on December 3, 1939, in the hands of the test pilot Doumerc. Evacuated to the new SNCASE factory in Marignane March 16, 1940, it continued his trials until the French surrender. It was then stored among LeO 451 in Istres in August 1940.
The Germans allowed the  testing in February 1941, it was  brought back to Marignane in May 1942. After a few test flights, work was started to receive new engines 14 R-4/5, in the form of "standard groups" including not only engines, but also radiators, accessories and standard covers "Bloch 174/175". But during the rebuilt in December 1942, an engine fire started immobilizing it for several months. Meanwhile, in retaliation for the Allied landing in North Africa  in November 1942, the Germans invaded the South zone and took control of the entire French territory, thus putting an end to the little autonomy of so-called "free" France.
The tests could not resume until the second quarter of 1943. From then on, all the planes were to wear the marks of the Occupant. LeO 455-01 received the code NT + HW. It is when confusion arises because, according to some sources, this code was also assigned to LeO 451 n ° 417, received by the Luftwaffe in Ambérieu and assigned to 8./ergTG.
After a few manufacturer test flights, the LeO 455-01 was transported to the Paris region on July 31, 1943 by SNCASO. According to German sources, iy was then seized by the Luftwaffe, inspected in August 1943 under the code GK + VD, then taken to Rechlin. However, this same plane is among the specimens destroyed in the rubble of the Marignane factory after the overnight bombardment March 9-10, 1944.
Two other LeO 451, n ° 584 and 602 were taken from the Ambérieu assembly line to be transformed into LeO 455 and used as
test benches for the Luftwaffe. These LeO 455 n ° 02 and 03 received respectively the codes CN + UX and NT + HX. Delays on these two planes only allowed 02 to fly before the end of the war, January 22, 1944. After a series of tests at Marignane, it was in turn taken by the Luftwaffe on April 28, to be assigned to IV./TG 4, under a new code also starting with GK + … As for the 03, it never flew under these colors, since it only took off for the first time in October 1945.

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