( CNN ) -- The wife of missing adventurer Steve Fossett has asked a court to declare him dead . Steve Fossett and wife Peggy in a February 2006 photograph . Fossett was last seen in early September , flying a single-engine plane on a pleasure flight from a Nevada ranch . A month-long search for the plane was unsuccessful . `` As difficult as it is for me to reach this conclusion , I no longer hold out any hope that Steve has survived , '' wrote Peggy V. Fossett in court documents filed Monday with the Cook County [ Illinois ] Circuit Court . She asked that the will of her husband of 38 years be admitted to probate . At about 8:45 a.m. on September 3 , the millionaire took off on what he said was to be a solo pleasure flight over the Sierra Nevada mountain range . He had planned to fly over the Nevada desert for two to three hours , and was expecting to return for lunch to the Nevada ranch , from which he departed . He was carrying a single bottle of water and had no parachute , lawyers for Mrs. Fossett said in the court documents . At 3 p.m. , when he had not returned , a search began that ultimately included thousands of volunteers . It continued until October 2 . `` No one involved in the search holds out any hope that Fossett is still alive , '' the petition said . Rick Rains , a sheriff 's supervisor of the San Diego County Sheriff 's Department , said Fossett 's plane was last spotted at 11 a.m. less than 20 miles from the ranch 's airport . `` Given the timeline and the sighting of Fossett 's plane , I believe he was within 20 to 25 miles of the ranch when he crashed , '' Rains said . But , he noted , `` the terrain is very difficult to search , with many areas where the crevices , deep ravines and closely grown trees make it impossible to see from the air what is on the ground . '' `` If Fossett was physically able to find water to survive on in the Nevada desert , he would have been physically capable of signaling searchers , by doing something as simple as crafting a large X of sticks or rocks , or by starting a signal fire , '' Rains said . In affidavits supporting his wife 's petition , Fossett 's doctor described the 63-year-old man as physically and mentally fit . Robert Keilholtz , a captain in the California Civil Air Patrol who was involved in the search , noted that the difficulty in finding wreckage was underscored by the fact that World War II-era plane wreckage was discovered last spring in the mountain range . In the search for Fossett , wreckage from eight other crashes was discovered , one of them from the 1960s , the lawyers said . Fossett made his money in the financial services industry , but is renowned for his daredevil exploits , which include nonstop , round-the-world trips aboard a balloon , a fixed-wing plane and a boat . At the time of his disappearance , Fossett was working on a project to build a single-man submarine and to build a vehicle capable of breaking land speed records by traveling at up to 800 mph , lawyers for his wife said . E-mail to a friend .
Steve Fossett missing since a solo flight over Nevada mountains . Single - engine plane last seen 20 to 30 miles from impact point , sheriff says . Plane not found after hours of search . Experienced aviator would have signaled rescuers if alive , sheriff says .