Factual error: The snake seen when they do the first survey is a reticulated python, which isn't native to the Amazon and also not deadly. (00:22:05)
Factual error: The way surveying is done is plain stupid. Percy Fawcett sets up a transit in the middle of a thick jungle, Henry Costin stands 10 feet in front of him holding the rod in one hand and a notepad in the other, then Percy looks through the transit and somehow reads the geographic coordinates out of thin air. This scene repeats couple of times during the movie.
Factual error: In the letter Nina Fawcett writes to her husband in case she dies during childbirth she mentions their unborn son. There's no way she could know the gender.
Factual error: An overhead shot of a passenger train supposedly before WWI shows a clip from the 1950s.
