Even if two Russians jets did indeed violate Turkish airspace (which Moscow denies), the intrusion would have lasted for just 17 seconds before one of the Su-24s was shot down, a leaked Turkish letter to the UN revealed.

Two Su-24 planes approached Turkish airspace on Tuesday morning, a letter addressed to UN Secretary-General Ban Ki-moon and the 15 members of the UN Security Council said.

The Russian planes are described in a document, published by WikiLeaks and Al Jazeera, as aircraft “the nationality of which is unknown.”