Pilots followed a trench across the Iraqi desert

Before GPS and advanced avionics, navigating a featureless desert from the sky was basically a high-speed guessing game. Imperial Airways solved this in 1924 by having a convoy of tractors plow a massive, continuous furrow directly into the Iraqi dirt. Pilots simply looked out the window and followed the 250-mile-long trench. If the wind blew the dust over it, you just prayed you were flying in a straight line.