Al Qaeda shot down a government warplane over the town of Al-Eis in northern Syria on Tuesday and captured one crew member alive, a rebel source and a monitoring group said.
The rebel source said it was "likely that (Al Qaeda's Syria affiliate) Al-Nusra Front shot down the plane and took the pilot," adding that the plane had been hit by heavy machinegun fire.
The Syrian Observatory for Human Rights said Al-Nusra downed the plane, which it said was likely being flown by a Syrian air force pilot.
The Al-Qaeda affiliate is not party to the ceasefire between government forces and non-jihadist rebels brokered by the United States and Russia that has been in place since February 27.
On Friday, Al-Nusra and its allies pushed regime loyalists out of Al-Eis, a strategic town in Aleppo province.
In video footage circulated on social media purporting to show the scene where the plane came down, a dozen men crowd around a man lying in the dirt.
Some of them cry: "He's Syrian, he's Syrian!" and others yell: "Get his weapons off him!"
AFP could not confirm the authenticity of the footage.
Last month, Islamist rebels shot down a regime warplane over the village of Kafr Nabuda in the central province of Hama.
AFP contributed to this report.