A United Express airplane headed to Portland, Ore. was diverted to Fresno due to a possible air pressurization problem.
The pilot called an in-flight emergency on Thursday.
The plane, which was carrying 60 passengers and four crew members, landed safely at Fresno International Airport.
SkyWest Airlines issued a statement saying, "SkyWest flight 6211, operating as United Express from Los Angeles to Portland, landed uneventfully in Fresno at approximately 8:40 a.m. after flight crews received an indicator related to the air conditioning system. Maintenance teams are in the process of examining the aircraft and we are working to re-accommodate the 60 passengers who were on board."