Danger stalks the West's mission of mercy: Steve Crawshaw joins a flight bringing humanitarian aid to Sarajevo

ALL FLIGHTS insist that you fasten your seat-belts and extinguish cigarettes before landing. But, on flight number 274, there was an additional requirement, a few minutes before the plane banked and dropped sharply through the clouds. Everybody had to put on a flak jacket.

Nobody on the plane needed reminding that the air route into Sarajevo is 'fragile', as officially described. The original flight path for the UN aid plane, as marked on the navigator's map, had been discarded: it meant too long a run into Sarajevo. More time for Serbian gunners to find their target. Out of the cockpit window, as the runway looms in front, a plume of smoke rises in central Sarajevo, marking the spot where yet another building has been hit by the gunners shelling from the hills.

A French relief plane has been shot at - though not seriously damaged. But the pilots of the daily relief flights, including flight 274, of the German air force, know they would be an easy target if anybody wants to make trouble.

On this flight there is a not untypical mix: sacks of wheat flour, cartons of margarine, cooking oil, cocoa powder, and dozens of boxes of surgeon's gloves. Around 15 tonnes in all. As fast as it arrives in the Croatian capital, Zagreb, the aid is loaded on to the UN planes that shuttle between Zagreb and Sarajevo, up to 20 times a day.

The relief operation for the besieged city was said to be too dangerous. But then President Mitterrand flew in - and helped the rest of the world to find the political will to make the operation work, despite the obvious risks. On arrival in Sarajevo, the cargo is distributed in the city by local drivers who risk their lives on each run. In Sarajevo, where most people stay off the streets, around 10 people are killed every day.

In the hangar the United Nations High Commissioner for Refugees (UNHCR) has made its home at the airport, sleeping bags lie among the cartons, which act as improvised bunkers - changing, from day to day, as the cartons are distributed. Dozens of aid workers bed down in conditions that are far from safe; some of the many bullet-holes in the windows were made in the last few days. On the walls, underneath the new UN posters, you can still see graffiti left behind by the Serbian forces who held the airport for many weeks: 'For Serbia, and Serbianness.'

The suburb of Dobrinja, adjacent to the airport, is still being fought over, and snipers are active. As you race down the road from the airport into the centre of Sarajevo, the bitter graffiti on one of many destroyed houses flash by: 'Welcome to Sarajevo.' This is still the world's most dangerous no-man's land. The only rule is that you drive twice as fast as common sense would ever allow. Windows are wound down, so as to remove at least the additional danger of splintering glass, if a sniper's bullet should pass through the car. A BBC vehicle this week was hit near the airport.

Meanwhile, aid workers, such as the representatives of the UNHCR, organise not just the distribution of aid in Sarajevo but also travel to the most inaccessible places - in eastern Bosnia, for example, where fierce fighting continues - in order to find out what is happening there. Sometimes, even the UNHCR cannot get through: yesterday, it complained publicly that the Serbian side had been 'unresponsive to repeated requests' to enter the besieged town of Gorazde in eastern Bosnia, in order to check the need for humanitarian relief.

Despite the undoubted courage of UNHCR workers, they do not tempt fate unnecessarily. Yesterday, however, a French aid worker was wounded by a sniper while standing near the Holiday Inn hotel, in an area that most of the hotel's guests - several dozen foreign journalists - would cross only at a brisk run, if at all.

Two journalists were lightly wounded in a separate incident near the same spot. The United Nations headquarters in Sarajevo, further along the same road as the Holiday Inn, has a postroom whose label accurately describes it as 'Snipers' Valley Post Office, Sarajevo'. Several destroyed vehicles stand outside the UN compound, where mortars landed on Monday night and again on Tuesday.