The film is set during the night. The disaster broke out at 6:26pm, three and a half hours before sunset.
Alfred Neubauer ordered the crew to make sure John Fitch is ready for his stint just before the disaster broke out. He was in the Mercedes trailer after a coffee with Pierre' Levegh's wife, just behind the pits by then.
There was a third Mercedes-Benz car, number 21 driven by Karl Kling and André Simon. The car itself appears briefly early in the film, but does not show up afterwards, and neither Kling nor Simon are seen or mentioned.
Alfred Neubauer did not have the authority to retire from the race. Such a decision had to be taken by the Mercedes board of directors in Germany. It took several hours for the directors to be called together, after which they issued the order to retire from the race. In the film, Fitch is shown arguing to Neubauer that the cars should be retired, and Neubauer refusing, at least initially. There does not seem to be supporting evidence for the fact that Neubauer was reluctant to retire the cars.
Despite starting the race late due to a technical difficulty, Fangio was actually in second position at the moment of the crash, behind Hawthorn in first. Shortly before the crash, Hawthorn had lapped Levegh (who was in 6th position) and Lance Macklin, who was also involved in the crash. In the film, Levegh is portrayed as challenging Hawthorn for the lead while Fangio is struggling to make his way up the field.