With early indications suggesting that the Bosnian Serbs haven't followed through on their Wednesday concessions, one of the key signals diplomats are awaiting is Saturday's scheduled opening of Sarajevo airport. Bosnian Serb leader Radovan Karadzic agreed to six concessions Wednesday and asked for the mediation of Jimmy Carter to help end the conflict in the former Yugoslavia. But a State Department spokesman said today that the U.S. is not "aware of any indications" that the Karadzic pledges have been fulfilled. One Karadzic's major concessions -- allowing U.N. peacekeepers free movement -- hasn't happened. Four aid workers are missing in Serb-held territory and relief convoys remain stymied in the northwest. Still, hoping against hope, U.N. officials said the airport reopening would be the real test. "There's still a skeptical wait-and-see attitude," says TIME United Nations correspondent Bonnie Angelo. Jimmy Carter apparently also has that same attitude: After a day of talks with U.S. officials, Carter still hasn't decided whether to head for Bosnia this weekend.Post your opinion on theInternationalbulletin board.