Joint Base Andrews conducts low-level helicopter training operations across areas in southern Maryland and northern Maryland including along the Potomac River.There are three separate low-level flight areas associated with training at NAS Patuxent River, two of which are in Maryland – East Helicopter Operating Area and West Helicopter Operating Area. Both low-level flight areas cover a broad area of land across Calvert County, Dorchester County, St. Mary’s County, and Wicomico County in which NAS Patuxent River conducts low-level flight training operations with rotary-wing and some fixedwing aircraft.Some military flight training is conducted at altitudes below 10,000 feet above mean sea level, and sometimes even below 200 feet AGL. For example, nap-of-the-earth training exercises include aircraft flying just above ground level or tree line using terrain-following sensors to avoid radar detection. Due to the low altitudes and speeds of the aircraft, these training missions are conducted within designed low-level flight areas to avoid collisions with civilian aircraft. However, the development of tall structures can interfere with and create hazards for aircraft conducting low-level flight training.