Shares of Boeing fell in premarket trade Monday, as markets digested the news that the Federal Aviation Administration had ordered a temporary grounding of dozens of Boeing 737 Max 9 aircraft.

Shares were down more than 8% in early hours trading by 5:05 a.m. ET.

The Federal Aviation Administration on Saturday said around 171 planes worldwide would be affected by its emergency airworthiness directive, which requires aircraft to be inspected before flying again. The order applies to U.S. airlines and carriers operating in U.S. territory.

It was issued after a piece of a plane blew out in the middle of an Alaska Airlines flight on Friday.

Images shared on social media showed a hole in the side of the aircraft and passengers using oxygen masks. The flight — Alaska Airlines Flight 1282 — returned to Portland shortly after departing for Ontario, California.

The National Transportation Safety Board has launched an investigation into the blowout.

“Safety will continue to drive our decision-making as we assist the NTSB’s investigation into Alaska Airlines Flight 1282,” FAA Administrator Mike Whitaker said in a statement.

Of the 171 aircraft grounded under the directive, United Airlines has 79 and Alaska 65, while the remaining 74 are spread across six other airlines. The 178-seater aircraft that suffered a blowout on Friday was delivered to Alaska Airlines on Nov. 11th.

Though large-scale groundings by aviation authorities are rare, the FAA has been keeping a close eye on the Boeing 737 Max since two fatal crashes almost five years ago forced the jetliner’s worldwide grounding.

Russ Mould, investment director at AJ Bell, noted that Friday’s incident is the latest in a “string of problems for the company,” and suggested airlines using 737 Max planes will be “thinking long and hard about their future aircraft requirements.”

Shares of Boeing’s European rival Airbus gained 1.7% by mid-morning on Monday as investors speculated that it could take market share from the U.S. powerhouse.

“There are naturally questions being asked about the quality checks and whether Boeing is trying to do too much too fast,” Mould said.

“Boeing’s management will be under considerable pressure from the regulators and customers to explain what’s going on, which means considerable headwinds ahead for the business. It’s no wonder investors have raced to sell the shares as the risks to the investment case have just shot up.”

This is a developing news story and will be updated shortly.

— CNBC’s Leslie Josephs contributed to this report.

The Federal Aviation Administration on Saturday ordered a temporary grounding of dozens of Boeing 737 Max 9 aircraft for inspections, a day after a piece of the aircraft blew out in the middle of an Alaska Airlines flight.

Images and video of Alaska Airlines Flight 1282 that were shared on social media showed a gaping hole on the side of the plane and passengers using oxygen masks before it returned to Portland shortly after taking off for Ontario, California, on Friday afternoon.

The FAA’s emergency airworthiness directive will affect about 171 planes worldwide and applies to U.S. airlines and carriers operating in U.S. territory, the agency said. Alaska and United Airlines said late Saturday that they were grounding their entire fleets of Boeing 737 Max 9s.

No serious injuries were reported on the flight, according to federal safety officials. There were 171 passengers and six crewmembers on board, Alaska Air said.

“Safety will continue to drive our decision-making as we assist the NTSB’s investigation into Alaska Airlines Flight 1282,” FAA Administrator Mike Whitaker said in a statement.

Large-scale groundings of aircraft by the FAA or other aviation authorities are rare. The FAA has heavily scrutinized the Boeing 737 Max since two fatal crashes grounded the jetliner worldwide almost five years ago. Two other models of the Max, the smallest and largest version, have not yet been cleared by the agency to enter commercial service.

The section of the fuselage missing appeared to correspond to an exit not used by Alaska Airlines, or other carriers that don’t have high-density seating configurations, and was plugged.

The National Transportation Safety Board has started its investigation. Chair Jennifer Homendy, at a press briefing in Portland Saturday night, asked the public for help in finding the plane’s missing door.

Homendy said no passengers were seated at the seat closest to the panel or the middle seat in the row where the door blew out and added that it was fortunate that the plane was still climbing and not at cruising altitude when travelers and crew could have been standing or walking through the cabin.

“We could have ended up with something more tragic,” she said.

The incident was described as “an explosive decompression at the window exit,” according to Sara Nelson, president of the Association of Flight Attendants-CWA, the labor union that represents Alaska’s cabin crew and flight attendants at United, Spirit and other carriers.

Anthony Brickhouse, a professor of aerospace safety at Embry-Riddle Aeronautical University, said such an incident is extremely rare.

“Rapid decompression is a serious matter,” he said. “To see a gaping hole in an aircraft is not something we typically see. In aviation safety, we would call this a structural failure.”

The incident is also a reminder to keep your seatbelt fastened when seated, he added.

“I always advise people on a commercial aircraft, keep your seatbelt on regardless of what the light says,” Brickhouse said.

Before the FAA issued its directive, Alaska Airlines earlier said it would ground its fleet of Boeing 737 Max 9 planes. On Saturday, the carrier said 18 of the planes “had in-depth and thorough plug door inspections performed as part of a recent heavy maintenance visit,” but later said it would temporarily ground them all.

“We are in touch with the FAA to determine what, if any, further work is required before these aircraft are returned to service,” Alaska said.

As of 7 p.m. ET, Alaska said it canceled 160 flights, affecting 23,000 customers.

The National Transportation Safety Board sent a team to Portland on Saturday to investigate the incident.

United Airlines, the largest operator of the planes in the U.S., had prepared to ground dozens of its Boeing 737 Max 9 aircraft for inspections, CNBC reported earlier. The carrier said late Saturday that it had grounded its entire fleet of 79 Boeing 737 Max 9 aircraft, after earlier saying 30 of the planes had already satisfied the FAA’s inspection requirement.

The FAA said the inspections will take between four and eight hours per plane.

The Boeing 737 Max 9 is a larger version of Boeing’s best-selling jetliner, the 737 Max 8. Max planes were grounded worldwide in 2019 after two fatal crashes within about five months of one another. The U.S. lifted its flight ban on the jets in late 2020 after software and training updates.

The Boeing 737 Max 9 has an emergency exit door cut behind the wings for use in dense seating cabin configurations, like those used by budget airlines, according to Flightradar24.

“The doors are not activated on Alaska Airlines aircraft and are permanently ‘plugged,'” Flightradar24 said.

Boeing didn’t comment beyond its statement when asked about the sealed emergency exit door. Spirit AeroSystems, which makes the fuselages for the planes, referred CNBC to Boeing when asked about the incident.

“Safety is our top priority and we deeply regret the impact this event has had on our customers and their passengers,” Boeing said in a statement on Saturday. “We agree with and fully support the FAA’s decision to require immediate inspections of 737-9 airplanes with the same configuration as the affected airplane.”

The company said it is supporting the NTSB’s investigation.

There are 215 Boeing 737 Max 9 planes in service worldwide, according to aviation-data firm Cirium. In addition to United and Alaska Air, other operators include Aeromexico, Turkish Airlines, Icelandair and Panama’s Copa Airlines.

Southwest Airlines and American Airlines operate the smaller 737 Max 8.

Late last year, Boeing urged airlines to inspect aircraft for a “possible” loose bolt in the rudder control system, the latest in a series of manufacturing flaws on Boeing jets that have prompted additional inspections, and slowed deliveries of the jets.

Airlines have seen a drop in bookings in the weeks following the start of Israel’s war against Hamas in the Gaza Strip, and some expect it to cut into their future profits.

According to travel analytics firm ForwardKeys, international flight bookings were 20% below 2019 levels in the three weeks following the attack by the Palestinian militant group Hamas against Israel on Oct. 7, and 5 percentage points below the period of three weeks prior to the attack.

The terrorist attack killed some 1,200 people and saw a further roughly 240 taken hostage, triggering the most ferocious Israeli response that the region has ever seen. Israel’s aerial bombing campaign and subsequent ground offensive in Gaza has killed more than 11,000 people, according to health authorities there.

In the days following the attack, major airlines suspended or reduced flights to Israel’s Ben Gurion Airport in Tel Aviv. But air travel demand to and from other countries and regions was noticeably affected, too.

In the three week period before Oct. 7, ticket issuance from the Middle East was just 3% below 2019 levels, according to ForwardKeys data, illustrating the steady recovery of the sector from the Covid-19 pandemic. In the three week period after Oct. 7, by contrast, ticket issuance from the Middle East was 12% lower than 2019 levels, marking a difference of 9 percentage points.

But the biggest drop in terms of international departures was in flight ticket issuance from the Americas, which was actually up 6% from 2019 levels in the three weeks before the attack, and fell to 4% below those levels in the three weeks after, totaling a drop of 10 percentage points.

International arrivals to the Middle East meanwhile plunged by 26 percentage points in that time frame, with the biggest drops by country being Israel, followed by Saudi Arabia, Jordan, and Lebanon. ForwardKeys draws its data from the International Air Transport Association’s industry-wide ticketing database which includes major international carriers, but does not include budget airlines like easyJet or Ryanair.

Stateside, at least one major airline made a profit warning concerning the war.

United Airlines in mid-October said that pricier jet fuel and a halt to its Tel Aviv flights due the Israel-Hamas war would eat into its profits in the last three months of the year. United had more service to Israel than any of the U.S.-based airlines with links from Washington, D.C.; Newark, New Jersey; and San Francisco, accounting for 2% of its capacity.

The fourth-quarter guidance for United was “bleak and worse than our estimates,” Helane Becker, an airline analyst at TD Cowen, wrote in a note following the carrier’s earnings estimate. “Given the projections that this will be a long war we are looking at the lower end of the forecast range and assuming no service by year end.”

The United Arab Emirates’ national airline, Abu Dhabi-based Etihad Airways, continues flying to Israel. It began flying its Abu Dhabi-Tel Aviv route in April of 2021, roughly eight months after the signing of the Abraham Accords, which normalized relations between Israel and the UAE.

“It’s impacting,” Etihad CEO Antonoaldo Neves said of the Israel-Hamas war, speaking to CNBC’s Dan Murphy at the Dubai Airshow on Monday. “Our demand to Israel is still there. But it’s not as big as it was in the past.”

“We keep flying, very safe. I follow up every day, every day. And we just hope it gets over soon. For the sake of everyone involved in this conflict.”

“I’ll not tell you it’s not impacting … And when things are back to normal, I’m sure that everyone’s going to remember that Etihad was not driven only by profits,” Neves said.

“We have our obligation as a transportation company, to be there when we make money and when we make less money. So that’s the approach we take, as long as it’s safe, we’re going to keep flying.”

Dubai’s flagship Emirates Airline, meanwhile, was optimistic about future demand.

“As far as the business is concerned — look, we have been in a part of the world that has seen for the last 35 years a lot of geopolitical issues,” Tim Clark, president of Emirates Airline, told CNBC.

“I won’t be smug and say we’re impervious to issues, because this is a really difficult issue for the Middle East to deal with.”

“But as far as our bookings are concerned, they remain robust,” he said. “We will always get what we call a certain flakiness in the Asian markets where, you know, they get a little bit concerned … But generally, so far, so good, we’re looking very strong.”

Clark pointed to upcoming events that will bring visitors to Dubai like the COP28 climate summit in early December as well as Christmas and New Year.

In a demonstration of its long-term optimism, Emirates Airline on Monday kicked off the first major deal of the 2023 Dubai Airshow with an order for 95 Boeing aircraft at a value of $52 billion.

“A lot of other things are going on in Dubai and Dubai itself is hugely potent city now, global metropolis, which is bringing in business,” he said.

“So with all of that, notwithstanding the difficulties of the Middle East at the moment, I think we will be okay.”

— CNBC’s Leslie Josephs contributed to this report.