What exactly happened when a Russian SU-27 fighter jet collided with a US MQ-9 Repear drone over the Black Sea remains in dispute.
What we do know, however, is the hi-tech unmanned Reaper is considered the most dangerous and deadly military drone in the world.
It's 11 metres in length and has a wingspan of 20 metres.
Controlled by aircrew on the ground, the Reaper has a maximum speed of 480km/h and range of 1850km, and can operate non-stop for 14 hours.
It takes 1.2 seconds for an operator's command to reach the drone via satellite link.
While mostly used for intelligence gathering, it's also America's front line hunter-killer drone, employing laser-guided bombs and Hellfire missiles to hit targets on the ground with precision.
It's claimed the onboard camera can read a number plate from 3.2km away.
It was used extensively in combat operations in Afghanistan and Iraq, and don't come cheap, costing about $56m each.
As well as the US, they are used by the UK, France, Italy and Spain.
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