"Stealth drone down" doesn't have the same ring to it as Blackhawk down, but this could be a game-changer anyway.
The Americans have lost an RQ170...
...an unarmed, unmanned recon aircraft launched by the USAF from Afghanistan but controlled by the CIA from Virginia, USA.
The Iranians now have it; it's on public display on Tehran. They claim it violated their territorial airspace. The Americans claim it was never flown into Iranian airspace.
The killer fact is this: the missing RQ170 did not crash - it's undamaged. The Iranians appear (and claim) to have taken over control, hacked it, and landed it. If they actually did this their capability is far in advance of anything anyone previously thought - especially the Americans - and completely changes the face of warfare. How long before a subverted Predator (a drone totting Hellfire missiles) is turned back and attacks friendly forces?