Government troops have been on the offensive for days near the Aleppo International Airport and a nearby military air base. The airport's director Bassem Mansour said it was opened after "sacrifices by the Syrian Arab army" who secured an area of 5 kilometers (3 miles) around the facility.
The Britain-based Syrian Observatory for Human Rights, which has a network of activists around Syria, confirmed that a civilian plane had landed.
Also Wednesday, the Syrian Justice Ministry dismissed a report alleging Syrian authorities tortured prisoners as "politicized and lacking objectiveness and professionalism."
The ministry's statement came after three prominent international war-crimes experts said they had received a huge cache of photographs documenting the killing of some 11,000 detainees by Syrian authorities.
David Crane, one of the three experts, told The Associated Press that the cache provides strong evidence for charging President Bashar Assad and others for crimes against humanity. "But what happens next will be a political and diplomatic decision," he added.
In the 55,000 digital images, smuggled out by an alleged defector from Syria's military police, the victims' bodies showed signs of torture, including ligature marks around the neck and marks of beatings, while others show extreme emaciation suggestive of starvation.
The report — which was commissioned by the Qatar government, one of the countries that are deeply involved in the Syrian conflict and a major backer of the opposition — could not be independently confirmed.
The Justice Ministry called the report a "gathering of images of unidentified people, some of whom have turned out to be foreigners of different nationalities who were killed while attacking military checkpoints and civilian establishments." It added that others were civilians and military personnel who were killed under torture by "terrorist groups allegedly for supporting the state."
The ministry said that the report has been revealed on the eve of the peace conference in a bid to "undermine the current efforts that aim to bring peace to Syria and end the international terrorism inside it."
More than 130,000 people have died in Syria's conflict, and more than a quarter of the population of 23 million now live as refugees, either within Syria or in neighboring countries.
The Observatory reported clashes Wednesday between government forces and opposition fighters in the suburbs of Damascus, Daraa in the south, Idlib and Aleppo in the north and the central province of Homs.
State news agency SANA says government forces battled "terrorists" around the country — including in the northern province of Idlib where fighters from Chechnya, Egypt, Turkey, Bosnia and Iraq were killed. State media always refers to opposition fighters as "terrorists."
Mroue reported from Beirut.