From Roger Ebert:

After opening with one of the most terrifying flying scenes I’ve witnessed, in which an airplane is saved by being flown upside down, Robert Zemeckis’ “Flight” segues into a brave and tortured performance by Denzel Washington — one of his very best. Not often does a movie character make such a harrowing personal journey that keeps us in deep sympathy all of the way.

Denzel Washington is one of the most sympathetic and rock-solid of actors, and it’s effective here how his performance never goes over the top but instead is grounded on obsessive control. There are many scenes inviting emotional displays. A lesser actor might have wanted to act them out. Washington depends on his eyes, his manner and a gift for projecting inner emotion. In the way it meets every requirement of a tricky plot, this is an ideal performance.

EW’s Lisa Schwarzbaum:

Played by Denzel Washington in one of the great performances of his commanding career, Whip is used to coasting on his tremendous talent and considerable charm, proud of his ability to “manage” his drinking and drugging. But during the investigation that follows the event, he engages in some desperate steering to postpone his own crash landing. How the man veers and buzzes, his cocky pride scrambling more and more wearily to outrun the truth, makes for a powerful and layered action thriller.

NY Times’ Manohla Dargis:

It’s no surprise that “Flight” has salvation in mind. The shock is how deep Mr. Zemeckis and Mr. Washington journey into the abyss and how long they stay there. It can be tough for stars to play such unrepentantly compromised characters, as Mr. Washington does brilliantly here. Most charm up their villains, thinning the venality with charisma and winks at the camera; in “Training Day,” as a seductively corrupt cop, Mr. Washington’s magnetism made a mockery of the story’s moral posturing. There’s no such falsity in “Flight.” The inevitable redemption doesn’t erase what happened or ease the pain, and the performance remains astonishingly true to Whip’s harrowing aloneness and its cost. Once again, you can’t take your eyes off Mr. Washington, but this time you watch him with agony rather than just admiration.