What was found
ON FLIGHT 4154, CREW REPORTED ENGINE VIBRATION IN CRUISE FLIGHT. PASSENGER REPORTED HEARING A LOUD BOOM NOISE FROM THE ENGINE IN FLIGHT. UPON LANDING IN ORD, THE TOWER REPORTED THAT EAGLE SHOULD CHECK THE NR 1 ENGINE DUE TO OBVIOUS DAMAGE AS SEEN DURING TAXI IN TO ORD. UPON POST-FLT INSPECTION, IT WAS DISCOVERED THAT THE NR 1 ENGINE COWL HAD OPENED IN FLIGHT AND PARTS HAD SEPARATED THE AIRCRAFT AND DAMAGE TO THE ENGINE HAD OCCURRED.