17 miles according to the Los Angeles Times. https://archive.ph/y5rY8#selection-1879.79-1879.93 16 miles according to the guardian. https://archive.is/MyhPN#selection-1667.49-1667.57 The crash site is about 19 miles from the airport, but the plane did indeed start descending at 17 miles. Kek.

17 miles according to the Los Angeles Times, but i've seen other articles stating a different distance. https://archive.ph/y5rY8#selection-1879.79-1879.93