A reconnaissance jet from RAF Waddington, near Lincoln, will be sent to monitor the crisis in Ukraine, the Ministry of Defence has said.
The UK E-3D Sentry Airborne Warning and Control System (AWACS) aircraft would carry out its mission while staying within Polish and Romanian airspace.
A NATO spokesman said the flights would “enhance situational awareness” and would only take place over alliance territory, which does not include Ukraine.
An MOD spokeswoman said: “The North Atlantic Council on Monday decided to employ AWACS reconnaissance flights over Poland and Romania, as part of the Alliance’s efforts to monitor the crisis in Ukraine.
“We have said that the UK will meet all our commitments under the next level of NATO crisis response measures.
“As the UK E-3D AWACS is part of the Nato AWACS force, then it is only right that the UK undertakes its share of this mission.”