Comments by "Neil of Longbeck" (@neiloflongbeck5705) on "What you Didn’t Know about the Amazing DC-3!" video.

You missed a bit of the story. It gets a bit James Bond. At the time they were designing the 247 Boeing did not have their windtunnel. The closest windtunnel were in California. The student running the tunnel Boeing was using to test the 247 design wanted to work in the aviation industry and so stole the test data and too, it to Douglas. Thus the DC-1 was also a cousin of the Boeing 247, which makes the DC-3 a second cousin once removed. Source: Widebody - the 747 story.
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During the Berlin Airlift a DC-3 was struggling to get airborne and to keep to time and altitude. After landing in Berlin it was discovered that it had been overloaded as it had been given the load for an Avro York. Shows just how capable the design was.
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