The Federal Aviation Administration (FAA) classified airspace over Nashville as “National Defense Airspace” in a temporary flight restriction and said the government could use deadly force against violators.

The FAA may take administrative action, including civil penalties and suspension of airmen certificates, and the federal government may place criminal charges against pilots who violate the restriction.

Deadly force may be used in some extreme cases.

“The United States government may use deadly force against the airborne aircraft, if it is determined that the aircraft poses an imminent security threat,” read the Notice to Airmen (NOTAM) issued on Friday.

The waring is effective until Dec. 30.