Hiding alone in a mountain crevice behind enemy lines, the injured American airman knew exactly what to do: survive and evade.For more than one day, the weapons systems officer whose F-15E Strike Eagle was shot down inside Iran avoided being captured by encroaching Iranian forces.At one point, he scaled the rugged terrain to a ridgeline more than 2000 metres above sea level, equipped with little more than a pistol, a communication device and a tracking beacon.READ MORE: Trump drops F-bomb