Alaska Airlines flight bound for San Diego was diverted back to Seattle after a strange vibration was reported on board, airline officials

An "unusual vibration" on a busy Alaska Airlines flight ended with a jet engine cover ripping off during an emergency landing at Seattle-Tacoma International Airport

Pilots turned the Boeing 737-900ER around, and then returned to the Seattle-Tacoma International Airport, where it landed safely, the airline reported.

A video posted on Twitter this week shows pieces of metal piece fly off a plane reportedly commissioned by Alaska Airlines.

The airline said there were 176 passengers and six crew members on board when the incident occurred.

"The two pilots who operated the flight have more than 32 years of combined flying experience," the airline wrote in its statement.

"They, along with our flight attendants, handled the incident with tremendous professionalism and care. We also greatly appreciated the patience of our guests during this event."

The aircraft is now out of service while the airline's safety team investigates, the airline reported.