Planning and training were how pilots were able to navigate the crowded airspace over Normandy. Most popular accounts of the D-Day operation were by paratroopers, not pilots, hence the complaints about poor navigation and supposed cowardice in the face of fire. However, night flying is always a difficult and risky endeavor, and the fact that so many aircraft were able to navigate across the English Channel with no visibility and few accidents is a significant feat of airmanship. The pilots were briefed about the route they would fly and told the specific altitude and speed their aircraft were supposed to fly, and flew using instrument flying, checking their gauges and using dead reckoning (because they would not have their navigation lights on to avoid ground fire) to approximate where their aircraft was. The mixed results of the night operation attests to how inexact this system was. Similar issues with crowded airspace happened in 1948 with the Berlin Airlift, and the commander of the operation ordered his pilots to strictly use instruments to maximize efficiency and safety.