Muslim soldiers hold a U.S. flag during a cease-fire in western Bosnia-Herzegovina. U.N. military observers trying to reopen Sarajevo's airport for emergency aid flights headed Tuesday for the Bosnian capital, where a fragile cease-fire held. A convoy of 50 U.N. vehicles carrying 60 observers was expected to arrive in Sarajevo from Belgrade. Sarajevo residents took advantage of a rare lull in the fighting to replenish food supplies, sharply reduced by a 2 1/2-month blockade by ethnic Serbs in the hills above the capital.