F-117 Kosovo Shootdown - Enemies become friends.

Zoltan Dani achieved a miraculous military feat: wielding outdated missile equipment, his army unit shot down an American F117 "stealth fighter" flying over Serbia as part of NATO's 1999 air strike assault.

The David-vs-Goliath victory was one of the most surprising achievements of the Serbian side as it was battered by NATO bombs that began dropping 20 years ago on Sunday, in a bid to halt Belgrade's war with Kosovo.

But in perhaps an even more remarkable twist, the retired army officer is now close friends with American pilot Dale Zelko whose Nighthawk he brought down.

"Bingo," Dani, now 62, recalls saying when he first learned he had struck the American aircraft, which was touted as invisible to radar.

The downing of the F117 three days into the NATO assault earned Dani national hero status.

It was the first and only time a F117 has been shot down in combat, leading celebratory Serbs to print shirts and posters with the slogan: "We didn't know it was invisible!"