That record for avoiding fatalities — which had never been approached in the history of modern aviation — was splintered in an instant Tuesday when an engine on a Southwest Airlines (LUV) plane exploded mid-air, spewing shrapnel into a window and killing a passenger.

“This is a tragedy, but it has now reached a state where it’s a one off, a fluke, an extraordinary event,” Stuart Matthews, who worked on reducing accidents for more than a decade as president of the nonprofit Flight Safety Foundation, said of the Southwest accident. “We shouldn’t stop flying or have other hysterical reactions.”

The last fatal crash on a U.S.-registered carrier occurred near Buffalo, N.Y., on Feb. 12, 2009, when a commuter plane operated by Colgan Air crashed, killing 49 on board and a man on the ground. The National Transportation Safety Board concluded a pilot overreacted to a cockpit warning, causing the plane to plunge, and the case prompted improvements in training.

Three people died on July 6, 2013, after a Korean-registered Asiana Airlines plane struck a seawall as it attempted to land in San Francisco. And two pilots died on Aug. 14, 2013, when a United Parcel Service plane landed short of a runway before dawn in Birmingham, Ala.

Tuesday’s death was the first in-flight fatality due to an accident in the 47-year history of Southwest. That doesn’t include a 2005 episode in which one of its jets skidded off a snowy runway in Chicago and onto a road, killing a 6-year-old boy in a car.

Few details have been released about Tuesday’s engine failure that led to the death. One of the most common jet engines around the world, a model known as the CFM56 that powers more than 6,700 Boeing 737s, failed so violently that metal shards struck the fuselage and wing, according to initial accounts by passengers and airport emergency responders.

One of the pieces shattered a window near where the woman was seated.

The aircraft, which Southwest acquired in 2000, last underwent maintenance April 15, Southwest Chief Executive Officer Gary Kelly said. There had been no issues with the airplane or its engines, he said. The engine that failed was last overhauled in November 2012, Southwest said.

“It’s overall way too early to give an answer as to what we might do,” Kelly told reporters at the airline’s Dallas headquarters.“We’ll be working with the NTSB to make sure we understand the root cause, and any further actions we need to take in terms of maintenance or inspections we’ll want to add to our program.”

The U.S. accident figures don’t include passengers dying of natural causes on board flights.

Aircraft engines have gone from an unreliable Achilles heel on planes in the 1950s to devices that can operate for millions of hours without so much as a hiccup, said Steven Wallace, the former head of accident investigation at the Federal Aviation Administration. That ranks it as the single greatest area of safety improvement in the last 70 years, he said.

Still, major engine failures in which debris escapes from the turbine’s hardened exterior shield remain a risk in aviation that regulators and accident investigators have focused on, Wallace said. While they’re rare, it’s hard to guarantee a plane’s safety when shrapnel starts flying, he said.

“It remains a matter of chance where that debris will go,” he said.

NTSB investigators examine three or four such cases a year, including incidents outside the U.S. on which they assist, said Chairman Robert Sumwalt as he prepared to depart for the accident site in Philadelphia.

While a concern, the last time an engine failure led to a death in the U.S. was almost 22 years ago. In that case, a Delta Air Lines plane, a McDonnell Douglas MD-88’s engine exploded, shooting debris into the cabin and killing two people on July 6, 1996.

Trump Tweet

Even more impressive is the stretch of fatal accident-free years in the U.S. The lack of a single fatality on a commercial flight last year prompted President Donald Trump to take credit for advances in safety in a Tweet that raised eyebrows in the aviation safety community.

“Since taking office I have been very strict on Commercial Aviation,” Trump said in a tweet in February. “Good news — it was just reported that there were zero deaths in 2017, the best and safest year on record.”

That didn’t include at least 13 deaths last year in seven crashes involving commercial charter flights in the U.S., and ignored the fact that the FAA was being run by an Obama-era holdover.

The trend toward safer flying has been building for years as U.S. regulators, the airlines and safety investigators brought on board new safety technologies, better monitoring of potential hazards and improved training. The improving U.S. accident figures don’t include passengers dying of medical emergencies.

“It’s very sad and I’m very conscious that this woman’s family has suffered a tremendous loss, but if you think about the industry, it’s the safest form of transportation ever built and it’s done nothing but improve,” said John Cox, a former airline pilot who is now president of consulting company Safety Operating Systems.

The NTSB and the FAA must get to the bottom of what happened on the Southwest plane and take steps to ensure it won’t happen again, which has been a key part of the formula for reducing risks in recent decades, said Matthews and Wallace.

However, people shouldn’t lose sight of the progress the aviation industry has made.

“The record remains absolutely remarkable,” Wallace said.