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NORAD
two U.S. Coast Guard MH-65D Dolphin helicopters will be employed during the exercise. Some portions of the exercise could involve flights at approximately 2,500 feet above ground level.
Never seen this source before:
https://wtop.com/national-security/2019/02/norad-plans-military-exercise-for-dc-area-on-wednesday/
A North American Aerospace Defense Command defense exercise is scheduled for Wednesday in the D.C. area.
Operation Noble Eagle is expected to take place between 4 p.m. and 6 p.m. During the exercise, NORAD said helicopter activity is likely to be visible. According to a NORAD statement, “two U.S. Coast Guard MH-65D Dolphin helicopters will be employed during the exercise. Some portions of the exercise could involve flights at approximately 2,500 feet above ground level.”