In a typical low-frequency radio instrument approach procedure, final approach would begin over the range station, with a turn to a specific course. The pilot would descend to a specified minimum descent altitude (MDA), and if the airport was not in sight within a specified time (based on ground speed), a missed approach procedure would be initiated. In the depicted Joliet, IL low-frequency radio approach procedure, minimum descent altitude could be as low as 300 feet AGL, and required minimum visibility one mile, depending on aircraft type.[22][23]