NATO is a mutual defense organization, which commits its members to defend each other if attacked by a foreign aggressor. Turkey has no obligation to lend any assistance to the U.S. in a military campaign overseen by a jug-eared Kenyan exchange student that is being waged for political purposes only. ISIS never attacked the U.S., and Turkey's leadership knows damn well that their involvement is only going to be used as a political tool in the U.S. to demonstrate the presence of a "coalition" in the U.S. military campaign.
What about when Turkey didn’t allow NATO jets to fly over their airspace during the war on Iraq?