Opposition group: ISIS militants training to fly warplanes in Syria

The former Iraqi military officers are among those who have joined ISIS, and people living near the airport have said they recently saw an airplane flying at low altitude after it took off, the observatory said.

ISIS has captured large swaths of northern and eastern Syria, as well as parts of western and northern Iraq, for what it says is its new Islamic caliphate.

This week has seen an increased number of U.S. airstrikes against ISIS in the northern Syrian city of Kobani, about 90 miles (145 kilometers) northwest of Aleppo.

The strikes are helping Kurdish fighters on the ground push back ISIS militants in the Syrian town, according to sources there.