A United Airlines aircraft bound for San Francisco was diverted back to Honolulu today due to a mechanical issue.

United Flight 372 carrying 351 passengers landed safely at the Daniel K. Inouye International Airport, said spokeswoman Maddie King.

The aircraft departed at 7:06 a.m. and landed back in Honolulu at 8:22 a.m. due to a mechanical issue with one of the engines.

The Boeing 777 aircraft returned to Honolulu “due to a report of smoke coming out of the right engine on departure,” according to Ian Gregor, spokesman of the Federal Aviation Administration.

A maintenance crew inspected it and the aircraft was returned to service. King declined to disclose additional information on the mechanical issue.

In an e-mailed statement, King said, “We’re working to get our customers to their final destinations as quickly as possible.”