Oil Leak, Improper Mission Planning Caused 2018 RQ-4 Crash July 20, 2020 | By Brian W. Everstine A leak in a cracked oil line caused an RQ-4’s engine to fail during a ferry flight to the Middle East in June 2018, and because the operations aircrews did not properly plan divert airfields en route, the Global Hawk crashed into the sea near ...