A Russian fighter jet dumped fuel on an American drone over the Black Sea and then collided with it, causing the drone to crash, the US military said. The aircraft involved were a Russian Sukhoi-27 fighter and an unmanned MQ-9 Reaper drone.

Here's your 5-point cheatsheet to this big story

1. The US uses the MQ-9 Reaper for both surveillance and strikes, and has long operated over the Black Sea keeping an eye on Russian naval forces.

2. Reapers can be armed with air-to-ground Hellfire missiles as well as laser-guided bombs and can fly for more than 1,700 km at altitudes of up to 15,000 metres.

3. An extended version of the MQ-9 has field-retrofittable capabilities such as wing-borne fuel pods and a new reinforced landing gear that extends the aircraft's already long endurance from 27 hours to 34 hours.

4. The Sukhoi-27 "Flanker", or Su-27, is a twin-engine, highly manoeuvrable fighter aircraft that provides air superiority. It was designed by Sukhoi Design Bureau.

5. Su-27s can operate autonomously in combat over hostile territory, in escort of deep-penetration strike aircraft and in the suppression of enemy airfields.