"Opposition fighters shot down a fighter jet that was shelling areas near Minnigh military air base... And the pilot's fate remains unknown," said the Syrian Observatory for Human Rights.
Rebels and troops have been fighting over Minnigh airport and other bases in Aleppo province for some two months.
The Britain-based Observatory also reported fighting near the international airport in Aleppo province, closed since January, and Nayrab air base.
The United Nations says more than 70,000 people have been killed in the violence in Syria since the uprising against Assad's regime erupted in March 2011.