Russian President Vladimir Putin has asked Britain to send experts to examine data from the black box belonging to the Russian warplane downed over the Turkish-Syria border last month, the Kremlin has said.
The request came in a phone call between Mr Putin and Prime Minister David Cameron early on Wednesday.
Downing Street gave no immediate details of the discussion, but a Number 10 spokesman said: "We are always happy to help and assist other countries on issues of security like this."
The Su-24 plane was shot down by Turkey as it took part in a bombing mission in Syria on November 24, with the death of a Russian serviceman as he parachuted from the aircraft.
Mr Putin has previously said he would like international experts to examine the black box data, which he believes will back up Moscow's denial of Turkey's claims that the plane violated its airspace after a number of warnings not to do so.
The black box was brought to the Kremlin on Wednesday by Russian defence minister Sergei Shoigu, who was told by Mr Putin not to allow it to be opened until international experts were available to examine it.