Several white orbs flying in perfect formation for 20 minutes

There were several white light orbs flying in a tight and almost perfect formation across the night sky at low altitude. There was a pattern in which each orb would flash its light in my direction, one at a time. They were flying in a direction and would disappear as more would keep appearing. This went on for close to 20 minutes. There were airplanes close by, sharing the airspace and there is an airport close by.