Alaska Airlines (NYSE:ALK) has taken the difficult decision to ground its entire fleet of 65 Boeing 737 Max planes after one of the jets encountered a midair emergency, leading to an emergency landing in Portland, Oregon.

The incident involved a 737 Max-9, which was carrying 171 passengers and six crew members. The aircraft experienced a “pressurization issue” shortly after takeoff, prompting the crew to return safely to Portland International Airport late Friday. The Federal Aviation Administration confirmed the issue in a statement.

Passengers aboard Alaska Airlines Flight 1282 shared images and videos on social media depicting a significant hole in the midsection of the plane. The flight was en route to Ontario International Airport in California when the incident occurred.

Before landing at 5:27 p.m. in Portland, the aircraft had ascended to a maximum altitude of about 16,000 feet and was traveling at a speed of 440 miles per hour, according to FlightAware, a flight-tracking website.

The FAA had certified the plane in November, and both the FAA and the National Transportation Safety Board will conduct a thorough investigation into the midair emergency.

“Each aircraft will be returned to service only after completion of full maintenance and safety inspections,” said Ben Minicucci, chief executive of Alaska Airlines (ALK), in a statement. “We anticipate all inspections will be completed in the next few days.”

Boeing (BA) recently recommended that airlines inspect all 737 Max jets for a potential loose bolt in the rudder-control system. During routine maintenance, an international airline discovered a missing nut on a bolt. Alaska Airlines (ALK) had stated that it expected to finish inspections of its entire fleet in the first half of January.