This was a 1980s film starring Roy Scheider of Jaws fame. He plays an LAPD cop who keeps having flashbacks of the Vietnam War.
Blue Thunder is infact the name of the helicopter he hijacks to exact revenge on a Government department who has gone against his way of thinking. The helicopter is nothing more than an Apache helicopter as used by the U.S Army.
Blue Thunder had infra red and 20mm cannons, which were things to marvel at in the early 80s but are now common place in modern warfare.