Revealing mistake: When Popeye's car stops chasing the EL train, there are skid marks from previous takes parallel to the ones that the car just made.
The French Connection (1971)
1 revealing mistake - chronological order
Directed by: William Friedkin
Starring: Gene Hackman, Roy Scheider, Fernando Rey, Tony Lo Bianco
Continuity mistake: When the drug tester gets done with testing the heroin, he blows out the lit candle on the bottom. But when there is a far shot of him talking, the candle is still burning.
Jimmy 'Popeye' Doyle: This is Doyle. I'm sittin' on Frog One.
Bill Mulderig: Yeah, I know that. We got the Westbury covered like a tent.
Jimmy 'Popeye' Doyle: The Westbury my ass! I got him on the shuttle at Grand Central, now what the hell's going on up there?
Trivia: James Caan, Peter Boyle and Steve McQueen were all offered the role of "Popeye" Doyle but turned it down for various reasons. Gene Hackman was eventually cast without auditioning, reading for the part or screen-testing.
Question: Why does Sal take the dirty car out of the city parking lot and park it by the docks? If that's the drug car why would the French let him do that?
Answer: The parking laws in the 1970's were not as strict as they are today, leaving a car on the street is no different from parking on the curb in a suburban area. The car was supposed to be picked up by the mob.