Which distance is indicated by a DME indicator?

The DME indicator provides slant-range distance in nautical miles, which represents the distance between the aircraft and the ground station. It is important to understand the term "slant-range," as it accounts for both the horizontal distance and the altitude of the aircraft. This means that the indicated distance is a straight-line measurement from the aircraft to the DME station, rather than just measuring along the ground or vertically up.

Other options, such as measuring vertical distance in feet or ground distance in nautical miles, do not accurately reflect how DME functions. DME does not provide vertical distance or direct ground distance measurements, but rather combines these factors into a slant-range distance that pilots can use for navigation and ensuring they are at the correct altitude relative to the station. This accurate representation is vital for navigation in en route flight, helping pilots maintain appropriate distances from navigational aids.