Here you see a Google Maps image of Aleppo International Airport, shut down from commercial flights since January, with several military helicopters:
The American Association for the Advancement of Science’s Geospatial Technologies and Human Rights Project studied satellite images of Aleppo and concluded, “A number of military helicopters were observed on the tarmac at the Aleppo International Airport. Their numbers and positions changed frequently, suggesting regular use.”
Yesterday the New York Times reported that “an American official familiar with the military planning said that the initial target list has fewer than 50 sites, including air bases where Syria’s Russian-made attack helicopters are deployed.”