‘A Money-Spinner:’ 737 Plane Model in Deadly Iran Crash Was a Bright Spot for Boeing

January 8, 2020, 10:22 PM UTC

A Boeing plane operated by Ukraine International Airlines crashed on Wednesday just outside of Tehran, Iran, killing all 176 people on board. The cause of the crash remains unclear.

In a statement, Boeing called the crash a tragic event. “We are in contact with our airline customer and stand by them in this difficult time,” it said. “We are ready to assist in any way needed.”

The crash will no doubt deepen the corporate crisis that’s ensnared Boeing for some 14 months now. It’s the third deadly crash of a Boeing aircraft since late 2018. The plane in Wednesday’s incident—the Boeing 737-800—is in the same family as the now-grounded 737 Max involved in the two earlier incidents, but aviation experts draw a distinction between the models.

The 737-800 is part of the Next-Generation (or NG) 737s that were introduced in the 1990s with increased wingspans, upgraded glass cockpits, and modernized interiors. The 737 Max, meanwhile, is categorized as a ‘fourth generation’ 737, because its design includes subtle tweaks to house more energy-efficient engines. The two fatal 737 Max crashes—a Lion Air flight in October 2018 and an Ethiopian Airlines flight in March 2019—came early in the model’s lifespan; it was only introduced in 2017. The decades-old 737NGs—of which the 737-800 is a variant—are proven workhorses that’ve carried billions of passengers across the globe. And until Wednesday, the family had been an undeniable bright spot for Boeing.

“It’s the most successful plane in the history of aviation,” said aviation expert David Learmount from FlightGlobal.

A child’s shoe is pictured on January 8, 2020 at the scene of a Boeing jet that crashed shortly after take-off near Imam Khomeini airport in the Iranian capital Tehran. (Photo by Borna GHASSEMI / ISNA / AFP)

As of February 2019, more than 4,900 models of the 737-800 had been delivered to airlines ranging from legacy carriers such as American Airlines and British Airways to European budget airline RyanAir.

In the wake of the 737 Max grounding that followed the two fatal crashes, the 737-800 has also played a vital role in supplying capacity for the global travel industry for the simple reason that with no new 737 Maxes rolling into service, airlines have had to hang onto their 737-800s for much longer than anticipated.  

“It’s a robust and reliable machine with great passenger appeal,” says Saj Ahmad, chief analyst at StrategicAero Research.

Leasing companies love it too. “[I]t has great residuals—which means that its value depreciates a lot slower than other competing airplanes in its class,” Ahmad says. It “commands a strong lease rate because of the demand from airlines. Many airlines renew leases, and—in some cases—buy them off leasing companies at the end of a contract if they choose not to extend,” Ahmad says

“In short, it’s been a magnificent money-spinner for Boeing,Ahmad said.

Dennis Muilenburg, ex-CEO of Boeing, addressed the families of victims who died in Boeing 737 Max jet crashes, during the House Transportation and Infrastructure Committee hearing examining the design, development, and marketing of the aircraft in October 2019. He lost his job two months later. (Photo By Tom Williams/CQ-Roll Call, Inc via Getty Images)

At the same time, the 737-800 doesn’t have a spotless safety record.

According to the Aviation Safety Network, the 737-800 involved in Wednesday’s crash was delivered to UIA in July 2016. It is just one of more than 7,000 variants of the 737NG planes to have entered service across 20 years. According to Boeing data, seven of the aircraft have been involved in fatal crashes.

That total includes a January 2010 Ethiopian Airlines crash, where 90 people died shortly after take-off in Beirut, and a Kenya Airways jet that suffered a similar fate in May 2007, shortly after leaving Douala in Cameroon, killing 114 people. As with the Wednesday incident near Tehran, the planes crashed shortly after take-off, although—unlike Tehran—both took off in poor weather. Official investigations into the two crashes pinned the blame on pilot error, with the Ethiopian Airlines pilot and co-pilot believed to have worked 51 consecutive days.

More recently, a 737-800 was involved in the March 2016 crash of a FlyDubai flight to the Russian city of Rostov-on-Don, which killed all 62 people on board. In September 2018, a 737-800 was also involved in a fatal accident in the Federated States of Micronesia, when an Air Niugini flight overshot the runway and wound up in a nearby lagoon, killing one passenger.   

All told, those incidents represent a small fraction of the millions of successful flights achieved by the aircraft.

“The first [737] flew in 1967, and it is still in production now in its Max variant,” says Learmount.

Ahmad says Wednesday’s crash has to be “looked at in isolation,” meaning it shouldn’t necessarily be tied Boeing’s ongoing 737 Max saga. That’s a tall order considering how the 737 Max crisis has plagued Boeing. Former CEO Dennis Muilenburg lost his job amid the scandal; in fact, his interim replacement was on the job when the UIA flight went down. His permanent replacement starts Monday.

At the same time, Wednesday’s crash near Tehran is unique in that it occurred amid escalating tension between Iran and the U.S., which is complicating the hunt for a definitive cause.

More must-read stories from Fortune:

—7 M&As that defined a decade of dealmaking and reshaped the economy
—3 charts that prove patent power is tilting in Asia’s favor
Rwanda is bringing tech buzz to Africa
—These 10 journalists deserve justice in 2020
2020 Crystal Ball: Predictions for the economy, politics, technology, etc.
Catch up with Data Sheet, Fortune’s daily digest on the business of tech.