He had loss of hydraulics and so could only steer and descend the aircraft by increasing and decreasing engine thrust. A true American hero!
He is indeed a true American hero -- and they forced him into retirement a few months after his amazing performance, due to his age. Silly. His long years of experience no doubt helped immensely when he had just a few minutes to invent and implement a method for controlling a large jetliner with no hydraulics. No sign whatsoever of mental decline. At the press conference the next day, he was calm, clear-headed, and philosophical, while his younger co-pilot sat in stunned silence, with the press having been informed in advance that he wouldn't speak at all.