The Ravens rallied for two late touchdowns in a span of less than 5 minutes and took a 21-20 lead on Joe Flacco's 9-yard scoring throw to Todd Heap with 1:05 to play.
Ryan then drove Atlanta 80 yards in seven plays and took just 45 seconds to do it. He hit Michael Jenkins with a 24-yarder out to the Atlanta 44, threw a 15-yarder to White and benefited from an interference penalty with 27 seconds left that put the ball on the Baltimore 33.
On the next play Ryan found a wide open White at the 15-yard line and White scored untouched. Baltimore defensive back Josh Wilson complained to no avail that he was pushed to the ground by White before the pass was thrown.
It was the third touchdown pass of the game for Ryan, who opened the scoring with a 28-yarder to Jason Snelling in the second quarter and also hit White with a 4-yard toss early in the fourth for a 20-7 lead.
Atlanta improved to 7-2 and took a one-game lead at the top of the NFC South over defending Super Bowl champion New Orleans, which is idle this week. Baltimore slipped to 6-3 and trails Pittsburgh by a half game in the AFC North, pending a meeting Sunday between the Steelers and New England.
Ryan completed 32-of-50 passes for 316 yards without an interception. White had 12 receptions for 138 yards.
Flacco was 22-of-34 for 215 yards and three scores.