These are the key factors investigators will examine to determine the cause of the Louisville UPS plane crash

CNN

By Lauren Mascarenhas, CNN

(CNN) — More than two dozen officials with the National Transportation and Safety Board are on site and have begun sifting through the mangled remnants of a UPS cargo plane that crashed after an engine detached during takeoff near Louisville Muhammad Ali International Airport.

They’ll try to determine what led to the disaster that killed at least 12 people while destroying nearby businesses and buildings.

The NTSB will release a preliminary report within 30 days, but it could be 18 to 24 months before the investigation concludes, according to Jim Brauchle, an aviation attorney with law firm Motley Rice and former US Air Force navigator.

In the wake of Tuesday’s tragedy, family members of the crash victims will be waiting for the answers investigators are working to uncover, Brauchle told CNN. In addition to the three crew members on the plane, nine community members have been reported missing and were believed to be in the area at the time of the crash, Louisville Mayor Craig Greenberg said Thursday.

“The one thing that all these family members, based on my experience, want to know is: How this could have happened?” Brauchle said. “It’s not something that happens every day, but I see it a lot. It’s more than grief.”

Here are some of the factors aviation experts say will be key to the investigation.

The crash site

The crash left a half-mile-long debris field, and the first priority is dealing with rescue and recovery, said Mary Schiavo, CNN aviation analyst and former Department of Transportation inspector general.

The debris field is large, though certainly not the largest the NTSB or similar agencies in other nations have encountered, she said.

“Crash investigators have scoured miles of Scottish countryside (PanAm flight 103), miles of ocean floor (TWA flight 800), and the southern Indian Ocean (Malaysia Airlines flight 370),” she said, referencing previous plane crashes. “They carefully map where pieces are recovered. There are great software programs that help you do this as you work a debris field.”

“Louisville looked apocalyptic,” Rep. Morgan McGarvey said at a news conference Wednesday. “The images of smoke coming over our city, of debris falling in every neighborhood, people trapped in their homes.”

“I had someone tell me it looked like it was raining oil in Louisville,” he added.

Two employees of Kentucky Truck Parts and Service, whose shop is located on the edge of the debris field, told CNN affiliate WLKY they were knocked back by the explosion.

“The flames were so bad. You can feel the heat,” said one of the men. “We made a decision: run for our lives.”

High fencing blocked their escape and the men remained trapped for around 90 minutes until police arrived with bolt cutters.

“There’s so much debris there, there’s so much charred, mangled metal, that not all the bodies may have been located underneath certain things,” Greenberg said Thursday on the search for more possible victims. “Going through the various layers (of) debris on the field, that will begin now. Everything to date has been just looking at what can be seen without moving debris.”

Though the plane was not carrying any hazardous cargo that would “create an environmental issue,” Beshear said, officials monitored Louisville’s air quality in the wake of the crash, according to the mayor.

Biohazards and chemical contamination are always present at the site of crashes, Schiavo said.

“When I work with crash debris, even months or years later, I wear hazmat gear,” she said.

The engine

The left engine of the plane detached during takeoff, NSTB member Todd Inman said Wednesday, citing airport surveillance footage viewed by the agency.

“Both the condition of the engine and the location of the engine will be of paramount importance to the NTSB,” Schiavo said. “The most recent maintenance will give a pretty good idea of the health of the engines.”

It’s possible pieces flying off of one failing engine could have impacted other key parts of the plane, and the engine likely ruptured the wing fuel tank when it ripped from the plane, she said.

The MD-11 is equipped with three engines: one on each wing and one on the tail.

While an image of what appears to be much of the left engine has been circulating, parts of the engine will likely still need to be found, CNN safety analyst David Soucie said Wednesday.

“If this engine did indeed come off prematurely, as it appears it did, then you’re going to be looking for the engine mounts. You’re going to be looking at the bolts themselves. All of those pieces need to be recovered and brought back in,” Soucie said.

The NTSB is asking people to report any debris found in surrounding areas, which could help provide investigators with some of the answers they’re searching for.

The black boxes

NTSB investigators have recovered the plane’s so-called black boxes – the cockpit voice recorder and the flight data recorder – which could hold crucial information about the moments before the disaster.

Black box recovery is critical, experts say, because the technology can point to what pilots were saying before a crash.

“It’s suffered some heat, not intrusion, but heat around it. These recorders are built for that,” Inman said Wednesday.

The agency will know more about what the black boxes contain once they are transported back to Washington, DC, Inman said.

Black boxes can survive a fire – but not always, Schiavo said.

Recent plane maintenance

NTSB investigators always look at three things when dealing with a crash: “They look into the environment. They look into the pilots. They look at the airplane,” CNN correspondent Pete Muntean, who is also a pilot and flight instructor, said Wednesday.

Since the weather was pretty fair at the time of the crash and the NTSB had few initial takeaways about the environment, the airplane itself will be key, Muntean said.

“The maintenance will be the big issue — what exactly was done to the aircraft, who did it, what parts were replaced, what procedures were followed, and who inspected the work,” Schiavo said.

Investigators likely requested all maintenance and overhaul records for the plane before arriving, she said. The team will be particularly interested in any maintenance checks, in which engines or other parts may have been removed or replaced, she said.

It’s too soon to know for sure whether any maintenance issues impacted the crash, Muntean stressed on Wednesday. Some of the initial videos and images from the crash are revealing, though, Schiavo said.

“The most telling photo is the one where the engine is separated from the rest of the wreckage, showing it separated from the plane before the final crash and explosion. This reveals the pilots were left with no ability to control this plane,” she said. “The fire on takeoff shows that something was wrong right from the start.”

The plane’s takeoff was not delayed, and no maintenance work was done immediately before the crash, according to UPS, Inman said. NTSB investigators will independently verify that and “will be going back and looking at every aspect of maintenance that was done on this plane,” he added.

The-CNN-Wire
™ & © 2025 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.

CNN’s Alexandra Skores, Amanda Musa and Carma Hassan contributed to this report.