After his aborted flight to the USA in 1936 in a Tupolev designed aircraft Levanevsky would not consider anything designed by him, thus when Stalin insisted he make the flight to the America, he selected the relatively untested 4-engine DB-A medium bomber. This was refitted, removing armament and adding capacity for more fuel and preparing it for this long distance polar flight. Perhaps that was one of the first missteps leading to the outcome we now know as the "Last Flight".