BRUSSELS, May 8 (Reuters) - NATO air policing units were put on a higher state of readiness following a near-miss between a Russian fighter jet and a Polish aircraft on patrol for the EU's border agency Frontex on Friday, a NATO official saidBRUSSELS, May 8 (Reuters) - NATO air policing units were put on a higher state of readiness following a near-miss between a Russian fighter jet and a Polish aircraft on patrol for the EU's border agency Frontex on Friday, a NATO official said