People across Mendocino and Humboldt counties looked up Friday afternoon after a large military helicopter flew low overhead. Flight tracking data showed the aircraft was a U.S. Army Chinook, passing near Willits before continuing north toward Humboldt County. The heavy-lift helicopter is often used to transport troops and equipment and can fly at lower altitudes, making it especially noticeable. No mission details were released, and military flights like this are considered routine in Northern California.