After the furore over its accidental attack on a refugee convoy, the alliance has changed its media strategy and admitted responsibility quickly, hoping the public will accept that in modern warfare tragic accidents are inevitable.
There is, however, concern at Nato headquarters about the amount of "collateral damage". One senior military figure last week said that, even with laser- guarded missiles or "smart bombs", a 10 per cent failure rate has to be expected. "We are doing better than that," he added.
As the alliance intensifies its air campaign, increasing its sorties and tackling more ambitious targets with a greater number of planes, the risk of accidental casualties grows.
The latest incident occurred when a bus was blown apart as it crossed a bridge in the town of Luzane, 20 km (12 miles) north of Pristina, at 1.15pm on Saturday. At least 23 people, including children, were killed and Serb media put the death toll at 60, although Nato yesterday said it was impossible to verify casualty figures.
On this occasion the two laser-guided bombs were not at fault, but the pilot who targeted the bridge had not seen the bus. At a press conference yesterday the alliance's military spokesman, Colonel Konrad Freytag, insisted the bridge was a "legitimate military target on a key re-supply route".
He added: "Unfortunately a bus was on the bridge but was not seen by the pilot. He did not target the bus and there was no intention to target civilians and any loss of innocent life is regretted."
The incident bears a striking resemblance to an earlier episode at Grdelica when, once the pilot's weapon had been released, he saw a train approaching the bridge.
Last week a stray missile hit a suburb of Sofia, the Bulgarian capital, causing damage and acute embarrassment if no casualties. On this occasion the authorities believe that the weapon was deceived by a Serb radar system which targeted a Nato warplane, forcing the pilot to attack the air defence unit before it fired at him. However the radar was then switched off, leaving the missile no "path" to its target.
"Weapon malfunction" has been responsible for several Nato accidents, including the bombing of Surdulica, a town near Serbia's border with Bulgaria, where at least 16 people died. Similarly, a technical failure was to blame for damage caused in a residential block after an attack on the Pristina telephone exchange. One particular problem in this campaign has been the weather: when there is cloud between a laser-guided bomb and its target, efficiency is impaired.
And, according to some estimates, as many as 15 per cent of Tomahawk cruise missiles will miss their targets.
However pilot error seems to have been to blame for some of the biggest casualties, in particular during the bombing of the refugee convoys which took place near Djakovica. During two separate attacks civilian vehicles were mistaken for military ones because army trucks are more difficult to identify accurately than tanks or armoured personnel carriers which have a more distinctive shape.