SARAJEVO, Bosnia-Herzegovina (AP) _ A French plane landed at Sarajevo airport today, testing a Serb promise to permit U.N. aid flights for the first time in five months in exchange for a halt in NATO airstrikes.

The military plane carrying Defense Minister Charles Millon was a dry run for U.N. aid flights to resume later in the day. The U.N. High Commissioner for Refugees said it was ``ready to go very, very quickly.''

Under an accord reached Thursday, the Serbs also agreed to pull back heavy guns menacing Sarajevo. It won the rebels a three-day reprieve from NATO bombing and gave new impetus to a U.S. plan to end 40 months of war.

The skies over Sarajevo were cloudy this morning, but NATO planes could be heard overhead. City streets were quiet but full of people, since Serbs have mostly refrained from targeting Sarajevo since the start of the NATO air campaign.

The commitment to let planes land in Sarajevo again was made by Gen. Dragomir Milosevic, commander of Bosnian Serb forces around the city.

Milosevic also agreed to allow the United Nations and international organizations use a road leading from the airport through the Serb-held suburb of Ilidza to Kiseljak, a neighborhood controlled by Bosnian Croats.

The Croats are allied with the Muslim-led Bosnian government.

The Serb concessions came after more than two weeks of NATO airstrikes and artillery attacks by the U.N. rapid reaction force. The attacked began after mortar attack on a Sarajevo market killed 38 people.

Serbs forced the airport to shut in April by making threats and attacking U.N. planes. The Serbs also have not permitted the United Nations regular road access to Sarajevo for months. That has forced soldiers, diplomats and aid workers to use the treacherous road over Mount Igman at the risk of Serb attack.

The accord was brokered by U.S. Assistant Secretary of State Richard Holbrooke, who met with President Alija Izetbegovic in the western city of Mostar today before leaving for Geneva for meetings with European diplomats.

The talks come at a critical juncture in peace efforts. The NATO raids, designed to force the Serbs to end their siege of Sarajevo, helped to produce an accord last week among Bosnia's warring parties over a possible future political arrangement.

Bosnian Serb leader Radovan Karadzic and military commander Gen. Ratko Mladic went to Belgrade to sign the agreement on Sarajevo in the presence of President Slobodan Milosevic of Serbia, a U.N. statement said.

Milosevic, the most powerful politician in the region and no relation to the Serb general, is negotiating for the Bosnian Serbs.

Some U.N. officials have criticized the section on heavy weapons withdrawal as too soft. Although NATO and the United Nations had originally demanded that Serbs pull back all weapons with a caliber greater than 12.7 millimeters, the deal permits Serbs to keep artillery up to 100 millimeters around the city.

The concession was sure to be seized on by critics who will accuse the international community of blinking once again in a confrontation with the Serbs.

The rebels seemed happy with the deal. Momcilo Krajisnik, the top aide to Karadzic, said it was the first step toward the ``just division of Sarajevo.''

Serbs want part of the capital and refused the original demand for a total heavy weapons withdrawal, saying it would leave sections of the city they hold unprotected. The government insists on having all of Sarajevo.

``Should the Muslims attack Serb Sarajevo, our army will have to activate its heavy weapons, which will not be far away,'' Krajisnik told SRNA, the Bosnian Serb news agency.

Under the terms of the agreement, the Bosnian government was to refrain from offensives in or around Sarajevo.

NATO bombing was to be suspended for 72 hours beginning Thursday. If the Serbs renege on the accord, the airstrikes are to resume. If the Serbs comply, the airstrikes will be suspended for an additional 72 hours to permit them to finish relocating their heavy weapons.

The Serbs pulled some heavy weapons out of the Sarajevo area once before, in February 1994, in response to a NATO ultimatum. That quieted the shelling of Sarajevo for months, but when no peace plan was put in place, Serbs raided U.N. depots where their weapons were stored and took them back.

Holbrooke's plan would give the Sarajevo government and its Croat allies 51 percent of Bosnia, and the Serbs, who now have about two-thirds, would get 49 percent. There still is broad disagreement on who gets what land.

Government forces and allied Croats advanced rapidly in western Bosnia this week, capturing several towns that likely would be given to them in a peace deal. Croatian and Bosnian media reported the two armies linking up today at Ostrelj, near Bosanski Petrovac.

U.N. officials say the Serbs, realizing they will have to give up some land, may be making tactical withdrawals instead of fighting for the towns.