The two cops wanted witnesses to corroborate what they were seeing, so they radioed for two fellow officers to come take a look at it, if for no other reason than to prove they hadn’t just been pranked by a couple of hopheads and alkies with 50 jars of Smuckers and absolutely nothing better to do.
Also a true story, kind of? Delta Force, a.k.a. The Greatest Movie Ever!
The plane was taken over by terrorists while en route from Athens to Rome, just like in the movie, and the rest of the film’s first half is a surprisingly faithful recreation of the TWA incident.
For example, in The Delta Force, the hijackers demand that the Jewish passengers be separated from the rest of the hostages and force a German flight attendant to sort through the passports to pick out the Jewish names, apparently because they assumed that all Germans are Nazis and are good at that sort of thing.
The hijackers did the exact same thing in real life to German flight purser Uli Derickson (who had a separate TV movie made about her a few years later). Rather than do what they asked, she hid all the passports and claimed she couldn’t find them.