As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT ATTENDANT REPORTED A HAZY SMOKE IN THE FORWARD CABIN THAT WAS DESCRIBED AS CHEMICAL IN NATURE WHLIE CRUISING AT FL 380. THE CABIN BECAME CLEAR AFTER APPROXIMATELY 2-3 MINUTES. THE -L PACK MODE- EICAS MESSAGE DISPLAYED DURING DESCENT TO FL 280. THE LEFT PACK TRIPPED AFTER LANDING. TROUBLESHOOTING FOUND THE LT ACM AT FAULT. THE LT ACM WAS REMOVED AND REPLACED IAW MM 21-51-03. LEAK AND OPERATIONAL CHECKS WERE GOOD.