A U.S. Warplane Shot Down a Syrian Jet. Here’s Why That’s a Big Deal.

An American warplane shot down a Syrian government fighter jet in the eastern part of the country on Sunday, in one of the clearest signs yet of an open conflict between the United States and the regime of Syrian President Bashar Assad.

The downing of the Syrian plane raises the possibility of future fighting between pro-Assad forces and U.S. forces that are deployed in Syria in support of Syrian militias battling the Islamic State.