The USS Truxtun guided-missile destroyer Friday crossed the Bosporus into the Black Sea to join the fleets of NATO alllies Rumania and Bulgaria in a naval exercise, the day after the Pentagon unveiled plans to put more US fighters on an air patrol mission over the Baltics. Additional US military exercises are planned for areas around the Russia starting Sunday. Twelve US F-16 fighter bombers and 300 military personnel are to be transferred to Poland over the weekend.