SEATTLE, WA - JANUARY 29: The tail and a next generation winglet of a A Boeing 737 MAX 8 are pictured at Boeing Field after its its first flight on January 29, 2016 in Seattle, Washington. The 737 MAX is the newest version of Boeing’s most popular airliner featuring more fuel efficient engines and redesigned wings. (Photo by Stephen Brashear/Getty Images) (Photographer: Stephen Brashear/Getty Images)

First flown in 1967, Boeing Co.’s 737 has become the world’s best-selling commercial aircraft. The fourth generation of jets made its debut in 2017 when Indonesian low-cost carrier Lion Air became the first commercial operator. Yet two fatal crashes within five months -- Lion Air flight 610 in October off the coast of Indonesia and Ethiopian Airlines flight 302 in March outside Addis Ababa -- have led to a global grounding of the aircraft, known as the Max, and put the 737’s previously sound safety record under the microscope.

1. How many airlines have purchased the 737 Max?

Plenty, but most orders have yet to be fulfilled. As of February, Boeing reported 376 deliveries of the single-aisle jets to 47 airlines or leasing companies. In total, orders from more than 80 operators exceed 5,000. Most sales are the Max 8, the model involved in both crashes. (There’s also, from smallest to biggest, a Max 7, 9 and 10.) The main operators include Southwest Airlines (31 in the fleet through February), American Airlines (24) and Air Canada (23). Norwegian Air, FlyDubai and several Chinese carriers also operate them. (Chinese airlines account for about 20 percent of 737 Max deliveries globally.) Click here for the full list.

2. How disruptive will the groundings be?

With fewer than 400 Max jets in service, not very, at least for most airlines. The global fleet comprised 24,400 planes at the end of 2017, according to Boeing. In the U.S., for example, the Max makes up about 3 percent of the mainline fleets for three carriers: American, Southwest and United. Some impact will be felt in Miami, where American has concentrated its initial Max deliveries for service to the Caribbean and to New York’s LaGuardia airport. Nonetheless, ticket prices may rise during peak season.

3. How do I know if my flight is affected?


Check your ticket; you should be able to tell from the booking details which plane you’re on. If you are making a booking online, many sites indicate the model. If not, websites such as flightstats.com allow you to dig into details of flights at least a few days in advance, including the make and type.

4. How is the Max different from earlier 737s?

It has bigger engines, incorporates more automation, has a higher range (up to about 3,550 miles, or 6,570 kilometers) and uses less fuel. Visually, the 737 Max differs from older models through its distinctive double winglets and serrated engine housing. Some reviews complained about the new design squeezing in smaller bathrooms and more seats. The Max was produced partly as a response to a new Airbus model, the A320neo. The Lion Air Max 8 that crashed was 2 1/2 months old, the Ethiopian Airlines jet just four months old.

5. Are the two crashes linked?

It’s too early to say. In both cases, the accidents took place not long after takeoff as the planes flew erratically and pilots asked to return to the airport. The investigation into the Oct. 29 Lion Air crash pointed to a malfunction of a safety feature -- the Maneuvering Characteristics Augmentation System -- that repeatedly forced the plane into a nosedive. The U.S. Federal Aviation Authority, which originally certified the 737 Max, initially elected not to ground it after the crash in Ethiopia, but dramatically reversed course three days after the March 10 accident. The FAA said satellite flight-tracking data combined with newly discovered evidence raised suspicions about the same feature implicated in the Lion Air crash. Ethiopia has sent the plane’s damaged black box to France, where it can be analyzed. Eyewitnesses say they saw smoke beforehand, suggesting something else went wrong.

6. What exactly is the MCAS?

It intervenes automatically when a single sensor indicates the aircraft may be approaching a stall. In the Lion Air crash, the pilots were baffled when the tool meant to stabilize the plane pushed the nose down multiple times, exerting more and more force until they lost control. All 189 people aboard died when it plunged into the Java Sea. Data suggested that the so-called angle-of-attack vane provided a faulty reading to the crew. Many veteran 737 pilots first learned of the flight-control changes in the Max 8 in the aftermath of the crash, and some were furious with Boeing for omitting any description of them from most flight manuals. Subsequently, the FAA and other regulators took steps to notify pilots of the MCAS and to remind them how to overcome it in the event of a malfunction. Boeing issued further guidelines on how to override the plane’s automated systems. The FAA said in March a more formal fix to redesign MCAS won’t be mandated until April. The Dallas Morning News reported that pilots in the U.S. repeatedly voiced safety concerns about the 737 Max 8 autopilot system to U.S. authorities months before the Ethiopian Air crash.

7. Were the airlines involved in the crashes safe?

While Africa has a generally poor aviation safety record compared with global norms, Ethiopian Airlines is known for operating a modern fleet that features Boeing 787 Dreamliners and the latest Airbus SE A350, as well as the 737 Max. The state-owned airline, Africa’s only consistently profitable carrier, has built Addis Ababa into a major hub feeding travelers from around the world into dozens of African cities in competition with rivals such as Dubai-based Emirates. Captain Yared Getachew had amassed more than 8,000 flight hours, according to the airline, while first officer Ahmed Nur Mohammod had spent about 200 hours aloft. The plane that crashed had flown about 1,200 hours. Indonesia’s aviation safety record has been criticized. Its airlines, including Lion Air, were banned from flying to the European Union and the U.S. for almost a decade until 2016 because of safety concerns.

8. What does this mean for Boeing?

Boeing has grounded its entire fleet of 737 Max aircraft, the company’s largest seller that accounts for almost one-third of operating profit. There’ll be claims from airlines; Norwegian Air said it will seek compensation for the grounding of about 1 percent of its seats. And it may impact sales; Lion Air and several other carriers have suspended deliveries or put orders on hold. In the two days after the second crash, Boeing lost more than $26 billion, or 11 percent, of its market value. Boeing issued a statement after the U.S. regulator grounded the aircraft saying it still has “full confidence” in the plane. According to an analysis of 47 commercial aircraft by Quartz, no other model has been implicated in as many fatalities as quickly as the Max 8 since 1966.

Some of these questions came from our readers via WhatsApp. You can sign up to get news and analysis from Bloomberg daily on WhatsApp here.

--With assistance from Paul Geitner.

To contact the reporters on this story: Kyunghee Park in Singapore at kpark3@bloomberg.net;Alan Levin in Washington at alevin24@bloomberg.net

To contact the editors responsible for this story: Jon Morgan at jmorgan97@bloomberg.net, Grant Clark, Christopher Jasper

©2019 Bloomberg L.P.