As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EWR - FLT 303 - EN ROUTE LGA-ORD, ON TAKEOFF AIR-CONDITIONING SYSTEM BEGAN EMITTING PURSUANT ODOR. CABIN FILLED WITH BLUISH SMOKE. AIR INTERRUPTED, DIVERTED EWR AND LANDED WITHOUT FURTHER INCIDENT. REPLACED APU OIL COOLER RING SEAL AT COOLER FITTING. ACCOMPLISHED PACK BURN OUT PER MM. ACCOMPLISHED LEAK CHECK. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)