As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT T1872/16APR UNABLE TO RETRACT NOSE GEAR. RED LIGHT ILLUMINATED WITH GEAR HANDLE IN UP POSITION ACCOMPANIED BY AIR NOSE. NOSE LANDING HEAR PIN WAS FLUSH. RETURNED TO ORD AND LANDED WITHOUT INCIDENT. REPLACED AND SERVICED NOSE LANDING GEAR STRUT. SYSTEM GROUND CHECKED NORMAL OPERATION. (CLOSED)