The Thrashers closed within four points of the eighth-place Buffalo Sabres in the playoff race with their second win in six days over the Eastern Conference-leading Flyers. Atlanta will face Buffalo on Saturday.
Danny Briere scored two goals, including a tying shot with 1:17 left in regulation for the Flyers, who overcame three one-goal deficits.
But goals by Schremp and Wheeler in the shootout finally gave the Thrashers a lead that couldn't be overcome. Ondrej Pavelec blocked Philadelphia's first attempt by Mike Richards, and Briere fired wide in the second round.
Trailing 3-2, the Flyers turned on the pressure in the closing minutes. Finally, Briere tied it up with his 31st of the season.
Ville Leino set it up by flipping a shot toward the net. Pavelec made the initial save, but Briere gobbled up the loose puck and put it just past the goalie's outstretched glove, even as Ron Hainsey planted the Flyers star face-first into the ice.
The game was back and forth all night. Tim Stapleton, Bryan Little and Nik Antropov scored for the Thrashers. Claude Giroux had Philadelphia's other goal, his 23rd.
Atlanta jumped ahead during 4-on-4 play in the first period on a shot that Flyers goalie Brian Boucher wished he could have back. Stapleton swept in off right wing and shot off a bad angle, the puck slipping under Boucher's pads as he slid across the crease, apparently anticipating a pass.
Philadelphia tied it before the period was done on a nifty bit of passing. Briere took the puck into the Thrashers zone along the boards, then ripped a pass to the middle of the ice for Andrej Meszaros pinching in from the blue line. The defenseman gave it right back to Giroux breaking in, and he beat Pavelec with a shot that trickled just inside the post.
Back came the Thrashers early in the second. Hainsey got off a blistering shot from the point, and Boucher made the save with his left pad. But he couldn't control the rebound, which was scooped up by Little and flipped over the flailing goalie.
Again, the Flyers tied it, taking advantage of a botched play behind the net by Pavelec. He came out of his crease to cut off the puck along the boards, and flicked it ahead to teammate Zach Bogosian. Only one problem: the young defenseman wasn't expecting it.
Jeff Carter scooped it up and passed in front to Briere, who buried his first goal with Pavelec all turned around and not knowing who had the puck.
Atlanta shook off that misplay to reclaim the lead again late in the second, this time when the Flyers inexplicably left Chris Thorburn all alone behind their own net. He tried to pass it to Radek Dvorak, who couldn't handle the puck. Not to worry — it went right to Antropov, who beat Boucher with a screened shot for his 13th goal.
Notes: Atlanta D Mark Stuart squared off with Philadelphia tough guy Daniel Carcillo early in the second period. Stuart got in some good rights to the side of Carcillo's head, before Carcillo countered with a punch that sent Stuart to the ice. ... Meszaros hobbled off after getting struck by a shot from the point with about 8½ minutes remaining. He quickly returned to finish out the game.