Foul play is not suspected after a man died on board a Boston-bound JetBlue flight Wednesday evening, officials said. The 77-year-old Newbury man had a medical episode, going into distress and becoming unresponsive while on JetBlue Flight 462 from Fort Myers, Fla., said JetBlue and Jake Wark, a spokesman for the Suffolk district attorney. Crew and passengers unsuccessfully attempted to provide medical assistance. The man was pronounced dead when he arrived at Logan International Airport just after 7:45 p.m. The man had medical conditions requiring the use of an oxygen tank, among other things, Wark said.