CHICAGO (Reuters) - Missing millionaire adventurer Steve Fossett was declared legally dead on Friday by a Chicago court five months after the airplane he was flying disappeared over Nevada, media reported.

His wife, Peggy Fossett, had asked Cook County Circuit Court in Chicago to make the declaration in November. Her petition for a judicial finding of his death said investigators had concluded that Fossett’s airplane was destroyed in a fatal accident.

“I believe the evidence is more than sufficient,” Judge Jeffrey Malak of the circuit court said in ruling declaring Fossett was dead, the Chicago Tribune reported on its Web site.

Citing court records it said his estate was “vast” and worth more than eight figures -- or multiple millions of dollars.

Fossett, a 63-year-old holder of several aviation and sailing records, vanished with his airplane after taking off from a private airstrip in western Nevada, one of the most remote and uninhabited regions of the continental United States, on September 3. An exhaustive search failed to find any wreckage.

British entrepreneur Richard Branson, who teamed with Fossett on some ventures and underwrote his successful global plane flight, said in September Fossett was scouting dry lake beds as locations for a future attempt to set a world land speed record.

Fossett, who earned his fortune as a financial trader, in 2002 became the first person to fly a balloon solo around the world and in 2005 achieved the first solo nonstop flight around the world in the Virgin Atlantic GlobalFlyer aircraft.

Last year Fossett flew solo in the GlobalFlyer to set the absolute nonstop distance record for any aircraft and set a new glider world altitude record with co-pilot Einar Enevoldson.

Fossett also competed in endurance competitions, swam the English Channel and set numerous world records in sailing.