Or maybe the character did.
Wouldn’t you agree, though, that that would be extremely out-of-character for an exacting engineer like Dorfmann?
If it was something that was obvious to the audience, or was corrected by a book immediately afterwards, then you can see it as significant. If it was like the HAL 900’s incorrectly stating the chess positions in 2001*, it would be a warning sign (to the seriously chess-savvy, at least) that something was wrong, and we should be alert that the character has something wrong. But this was a throwaway line at the end of the movie. There’s no point in having it inaccurate. I suspect the screenwriter of laziness.**
*I have to admit that I missed this, myself, in all my viewings of the film. I only know about it because they point it out in Benson’s book Space Odyssey, which I just finished.
**It’s been too long since I read the book, and I don’t recall whether it’s in there or not. I suspect not.
Facts matter. If Dorfmann is lying (or wrong) about that, how can we, the dying survivors, trust him that he can build a plane? A “properly designed plane”?
(I admit I would have went along. What else could you do? Chances are they would crash. Not doing anything also will kill you.)
The fact that mattered in the film is that if someone knows how to build a flyable airplane, then the airplane will fly. It doesn’t matter at all who built a flying model 100 years ago, since flying models had been around for a very long time. It was demonstrated that airplanes can fly without pilots. That was Dorfmann’s point, and the fact that mattered.
Be that as it may, in a huge desert how would anybody find the buried body of the tribesman, and if everybody agrees to just shut up about it, nothing will happen. I am sure that during the ‘fog of war’ many ‘executions’ end up happening that never get mentioned by the people involved … not that I condone it, but really - us vs them, us is going to win in a survival situation. I know if it we mrAru and I as the us, and some random guy that had just been attacking, mrAru has a shovel and I have a closed mouth on the situation [I may have been the one to do the shooting, who knows.]
“Will I get caught?” is a completely separate question from “Is it legal to kill this guy?”
How is *that *the point at which your suspension of disbelief suddenly stalls and crashes? 
Did I say anything about my willing suspension of disbelief being disrupted? I can be annoyed at an erroneous line without that serious a result.
So as long as the point is made, it doesn’t bother you that they say other things that are completely and easily provable to be incorrect?
I won’t be reading any historical novels you write.
This is what’s wrong with the country today. “Who cares about facts? As long as your intentions are good, facts don’t matter.”
The only evidence the survivors have that Dorfmann knows what he is doing is his word. And Dorfmann is attempting to prove he knows what he is doing by citing untruths.
Dorfmann comes across like he knows his stuff. He’s obsessed with details. He does the calculations, he designed the plane. But he lies about something that doesn’t even matter!
There really is a difference between a model aeroplane and a full size one. They don’t scale. Dorfmann was ultimately proved correct - he made a plane that would work. But considering what happened to Mantz IRL flying the plane, he was lucky more than smart.
It’s an error made by a character. A character who thought his life depended on convincing the other character. I’m inclined to give it a pass.
I’ve already posted I would have helped build the plane. I maintain Dorfmann wasn’t as smart as he thought he was, but he was smart enough.
But Dorfmann was still a jerk. Towns wasn’t much better. No, correction: he was worse, actually. Aside from getting them into the mess in the first place, and bad resource management after the crash, he fought Dorfmann over politics, not engineering. Towns needed to feel he was the leader. He would have led them to their doom.
Stratolaunch just rolled out The Largest Airplane in the World.
I just looked at that construction, and my first thought was “Hey – they could do another remake of Flight of the Phoenix with that!”
Better have two engineers this time…one aero-space and one network/infrastructure/systems guy (who just happens to have the access codes and software to get into the onboard systems and can reprogram them). 
Not to mention rebuilding a much heavier system that’s not made out of steel but out of complex composite materials be possible? I suspect your problems would be much bigger than the angled fittings facing the wrong way, and that rebuilding would involve more than removing a couple of big pins and hammering them in to the other side.
But it’s a thought.
I’m guessing “no”. Maybe they could have built it, but I doubt the aircraft or the passengers would have survived the flight.
I can’t address the materials part as I have no idea. Could you stitch together the composite skin with drilled holes? No idea. But, as with my earlier comment, I think the control surfaces would be a nightmare. In the case of this plane you’d need to access the internal systems, reprogram them, run control lead after you test and then ensure your fly by the wire system (I assume it doesn’t have a redundant backup analogue system) works as you want it too. In some ways it would be easier, assuming you had the right access and right knowledge, but in other ways it would be a stone cold bitch. If one of the people on board knew pretty much how the system works, how to program it (and shut off parts of it or reprogram alarms or expert systems designed to help that wouldn’t be much help in the new system), how to just authenticate to gain access and maybe knew enough about it to also be able to re purpose large parts of it then it would just be a matter of salvaging the stuff you’d need (and powering it of course). As with the earlier scenario wrt the movie (I only saw the first one) my skepticism is more of whether they would have time and also, without a lot of testing, how reliable the thing would actually be. Hell, without a wind tunnel and some balance tests, I’m not sure you could redesign something like this in your head to account for everything and get something that works well enough to fly hundreds of miles and land safely (defined as walking away).
The crashed aircraft is allegedly a Fairchild C82A Packet, but from the photos I see it has minimal tailpiece stabilizer control on the outboard edges.
It’s been 40 years since I read the book, is this addressed? Glossed over? Pretend it was a better aircraft?
My beef was the undercarriage. They weld metal bars to make skis, or as Dorfman refers to it a “Skid Cradle”. I know planes use skis on ice but sand?? Can a plane overcome the friction to even taxi on that kind of surface?
The design and construction of the plane in the movie took 5-6 months in a workshop specifically equipped to build prototype planes.
While the wings of the movie aircraft were from a Beechcraft and the engine, cockpit and controls and undercarriage from a T-6 Texan, the fuselage, empennage and wing roots (where the wings are attached to the fuselage) were custom designed and built.
No chance of making this work without any machining tools (lathe, milling machine, machines for sheet metal working) in the middle of the desert.