If you hear large aircraft in the skies above Washington overnight, it’s likely a military exercise testing the region’s air defenses.

The North American Aerospace Defense Command says the flights are scheduled to take place between 11:30 p.m. Wednesday and 5 a.m. Thursday.

NORAD regularly conducts such exercises, known as Falcon Virgo, to hone operations and test the region’s visual warning system.

In the event of inclement weather, the exercise will take place Thursday into Friday.