In 1919, the RAF opened regular aerial lines between London and Baghdad. It passed by Alexandria, Heliopolis (Cairo), Gaza (Palestine), Amman (Jordania) and then arrived at Baghdad. The main rest stop in the Iraki desert was Rutbah Wells which was an old legionnnary fort. There was no radio transmission in the airplanes in those times. So the Brits made a visual guide by making dig a 800 milles long furrow that the pilots could follow safely during their flight. This furrow was regularly filled because of sand storms, so it had to be cleared by hand very often. As you can see on this painting, the service was provided by RAF aircrafts because the Imperial Airways didn''t exist yet : at the end of the day, two Vickers Vernon are arriving at Rutbah Wells...