01 alaska airlines engine cover
CNN  — 

An Alaska Airlines flight bound for San Diego was diverted back to Seattle shortly after takeoff Monday morning, according to a statement from the airline.

Flight 558 “reported an unusual vibration on the left side of the aircraft soon after departure,” a representative for Alaska Airlines said in the statement to CNN. “The aircraft returned to the airport and landed safely.”

The flight took off from Seattle-Tacoma International Airport at 7:36 a.m. local time and was back at the airport by 8:04 a.m., Alaska Airlines told CNN Travel.

Part of the cowling (a removable metal housing for the engine) detached from the plane when it landed, according to the airline.

‘Heard a little pop’

This is a picture Alaska Airlines passenger Greg Anderson took on Flight 558 on Monday morning.

Passenger Greg Anderson was on board Flight 558 on Monday and took photos showing the damage to the plane’s left engine.

He told CNN the plane took off normally and then he “heard a little pop” and felt the plane start to vibrate.

Anderson said he could see pieces of the cowling coming off.

“We slowed way down then the captain came on and said he felt an ‘unusual vibration,’ and we were told he was looking for a place to land,” Anderson said.

He said more of the cowling fell off as the plane was landing.

No injuries were reported among the 176 passengers and six crew members on board at the time, the Alaska Airlines statement said.

Guests were moved to a new flight to San Diego, which departed about two and a half hours after they got back to the gate, the airline said in an email.

Anderson said he was booked on another flight and got to San Diego about 1:30 p.m.

Experienced pilots

Alaska Airlines praised the crew onboard.

“The two pilots who operated the flight have more than 32 years of combined flying experience,” the statement said. “They, along with our flight attendants, handled the incident with tremendous professionalism and care.”

According to the airline, the Boeing 737-900ER plane is out of service while a safety team investigates the cause of the issue.

Top image: Damage to the Boeing 737-900ER (courtesy of Greg Andreson).

CNN’s Forrest Brown contributed to this report.