Düsenflieger is a fantastic German compound word, combining Düse (jet / nozzle) and Flieger (flyer / plane). It's a much cooler way to say "jet fighter"!
In the song, the story takes a turn when the military scrambles 99 Düsenflieger to intercept what they think are UFOs, but are really just balloons. This word perfectly captures the Cold War paranoia and military overreaction that is central to the song's powerful anti-war message.
This song tells a wild story that starts so simply. The singer begins a song for someone special about 'neunundneunzig Luftballons' (ninety-nine balloons) floating towards the horizon. But this innocent sight causes a huge misunderstanding. Someone spots them and thinks they're 'UFOs aus dem All' (UFOs from outer space), so a general sends up a squadron of fighter jets to check it out.
From there, everything escalates ridiculously fast. The pilots, each thinking he's a 'großer Krieger' (great warrior), shoot down the balloons. This makes the politicians, the 'neunundneunzig Kriegsminister' (ninety-nine war ministers), see a chance to grab power. And just like that, a handful of party balloons starts a 99-year war that leaves the world 'in Trümmern liegen' (lying in ruins). It's a powerful anti-war song that shows how a small, paranoid mistake can lead to total destruction.