Twenty-five British soccer fans were flown aboard a Belgian air force plane to Brussels to face investigation and trial in the deaths of 39 people in a 1985 stadium riot. The fans, all from Liverpool, were accompanied by a Belgian police guard on the flight from Britain. They were taken to the Palace of Justice for preliminary questioning by a magistrate and were expected to be sent to a specially reserved wing of Louvain jail, east of Brussels, pending results of the investigation. Belgian officials said charges could range from aggravated assault to manslaughter. A trial is not expected before December. Inmates at Louvain and at other prisons have rioted recently over alleged special treatment planned for the Britons.