Inching towards a clash?

 Jonathan Marcus, BBC defence and diplomatic correspondent

What happened on Monday is only the latest incident in a continuing pattern where Russian and Nato aircraft have come into close proximity.

The two sides' narratives are very different but independent studies have tended to support Nato's case that more aggressive Russian behaviour is in large part to blame - this a response to Nato's stepped up military deployments in central Europe in the wake of Russia's seizure and annexation of Crimea.

These tensions risk accident and injury but are very different to the situation in Syrian airspace where the US, its coalition allies and Russian and Syrian warplanes are all engaged in combat sorties.

Unlike in Europe, there is a direct link between Russian and US commanders to avoid dangerous incidents - and although Russia is saying that this has been suspended in the wake of the US shooting down of a Syrian jet - the US side insists that the channel remains open.