Pilots in the early days of aviation relied on dead reckoning to find out where they were flying, which proved difficult or impossible at night or in bad weather.[3] A 1925 United States Post Office study found that 76% of its forced landings were due to weather, which highlighted the early need for a system to facilitate blind landings. Early suggestions at addressing the problem ranged from using primitive radio signals[4] to placing emergency landing strips periodically near major highways.[5] Experiences from the Second World War called more attention to the problem. Bombers based in Britain would sometimes return to their home bases in the early morning hours to find all of their landing sites completely fogged in, which resulted in the senseless loss of airframes and aircrews.