When one of Europe's most lethal terrorists shows up in New York, an elite undercover cop is assigned to take him down by any means necessary.
 
The meaning and relevance of this movie's title is that "Nighthawks" refers to the men and women street cops of the New York City Crime Unit who patrol the city at nighttime.  I tell you this because you pretty much already know what to expect from this movie and would probably prefer some clarification on the film’s title instead. 
 
FUN FACT:  Sylvester Stallone said of the cable-car stunt to "Ain't It Cool News": "Hanging from the cable car was probably one of the more dangerous stunts I was asked to perform because it was untested and I was asked to hold a folding Gerber knife in my left hand so if the cable were to snap, and I survived the two hundred thirty foot fall into the East River with its ice cold eight mile an hour current, I could cut myself free from the harness because the cable when stretched out weighed more than three hundred pounds. I tell you this, because it's so stupid to believe that I would survive hitting the water. So to go beyond that is absurd."