Writer-director Paul Greengrass’superb 9/11 docudrama United 93 is one of those movies that should be seen, but it’s understandable that many viewers won’t want to see it, and no amount of critical hosannas will change their minds. We all know the tragic yet inspiring saga of what happened on this particular airplane on that fateful September day. United 93 takes us through the morning’s activities, beginning with the terrorists praying at dawn and hopscotching through various air traffic control rooms scattered along the northern corridor of the country as well as the Federal Aviation Administration HQ. The first half of the movie spends more time with traffic controllers desperately trying to make sense of the chaos descending on them at sickening speed. Monitoring the blips on the screens, the controllers begin to sweat when particular ones veer off course or disappear. And then there are those reports that smoke is emanating from one of the World Trade Center towers, in the vicinity where one flight’s location was last verified. Surely one has nothing to do with the other? The implications sicken the characters as much as it churns up roiling emotions in viewers who know how this will all turn out. In the second half of the film the connective tissues of the story fall away, and we’re exclusively left with the saga unfolding aboard United 93. Realizing that these terrorists plan to use the plane as a weapon of mass destruction -- and thereby realizing that no Entebbe-style rescues will be in the works -- the passengers decide that only they can stop the murderers at the controls. It’s noble to imagine that their collective motive was to honor and protect God and country, but this movie is honest enough to acknowledge that, like any of us caught in such a situation, self-preservation comes first. And it’s a testament to the movie’s power that we find ourselves praying for a safe landing even though actual history has long dictated otherwise. Greengrass repeatedly refuses to take the bait of making a picture that can be tagged as exploitive, propagandistic or too political. How restrained is Greengrass’ approach? Understand that passenger Todd Beamer’s catchphrase "Let’s roll" -- you know, the one that’s been co-opted by seemingly every politician, pundit and newshound from coast to coast -- is barely audible when Beamer speaks it in the film, and even then it’s not a stand-alone quip but rather part of a string of hurried utterances.