The circular contrail sighted over Durango early Friday afternoon was created by a military plane, the Federal Aviation Administration said Monday.
In answer to a request for information, the FAA office for the Northwest Mountain Region in Renton, Wash., said by email that the plane was 15 miles west of Durango. The pilot made a 360-degree turn at 1:09 p.m.
This aircraft was at 38,000 feet, which probably contributed to a dense contrail. The turn was tight. It was completed within a 15-mile diameter. Nothing unusual or unsafe.
A request for more information was referred to the military.