A Delta Airlines McDonnell Douglas MD-90, performing flight from Milwaukee to Atlanta (USA) with 164 people on board, reported lightning strike causing engine vibrations.

• Aircraft was enroute at FL250 about 25nm westnorthwest of Chattanooga (USA) when the aircraft reached a frontal weather system and received a lightning strike.
• The left hand engine (V2525) began to vibrate prompting the crew to reduce the engine to idle and to divert to Chattanooga for a safe landing on runway 02 about 25 minutes later.