At least nine individuals lost their lives and 11 left injured following a UPS cargo plane crashed during departure from an international airport in Kentucky's largest city on Tuesday night.
Aviation experts believe the aircraft went down due to a single engine malfunctioned and a second seemed compromised while lifting off.
The exact cause remains unknown what caused the plane to crash, leading to a huge explosion to ignite after it failed to take-off from the runway. Footage revealed fire had already engulfed one wing of the aircraft while it was attempting to take off, which may have spread through the plane and triggered the blast, or the plane might have ignited upon hitting an object on the ground.
What's clear is that the 38,000 gallons of jet fuel aboard the trijet aircraft needed for the flight probably intensified the fire, which quickly spread to multiple structures past the airstrip and continued burning for hours.
How did it start?
UPS operates from the Louisville air hub as a logistics center for its global operations and its Flight 2976 was at the start of a 4,300 mile trip to Honolulu in Hawaii when the freight aircraft initiated departure.
Data from FlightRadar24 shows the plane started moving along the 17R runway at around 17:15 local time and managed to reach a maximum velocity of 214mph.
But verified footage shows that by the time the plane reached this speed a blaze had fully consumed its left wing and the aircraft failed to gain altitude before the massive explosion.
Officials activated a shelter-in-place order to area inhabitants and dispatched numerous fire crews to the scene.
The state's governor confirmed details visible in security camera recordings that shows the aircraft flying just metres off the ground before a bright flash engulfed the plane. It is then observed crashing onto the ground as a massive fire explosion ignites surrounding it about a minute after departure.
A verified clip recorded by motorists on a nearby highway displayed the fire rising into the air while subsequent recordings revealed smoke pouring from the area.
Aerial images shown on local media depicted debris showering the runway and falling onto the tops of multiple nearby establishments.
What could have caused the crash?
Air traffic control communications examined are mostly unclear and full of interference so no meaningful conversation can be discerned about the crash as it unfolded.
But analysts suggested that a dramatic failure of multiple engines may have been responsible for the tragedy.
The MD-11 transport plane uses three powerplants. Two are mounted under the airfoils, and a third is built into the tail at the bottom of the tail fin.
Footage confirmed showed a blaze engulfing the port wing of the plane, which then tilted to the left as it attempted to gain lift and take-off.
Two experts independently suggested the portside engine may have detached from the plane following a mechanical or structural failure.
Additional photographs taken after the crash displayed a burned powerplant sitting on the turf adjacent to the airstrip.
An experienced former aviator and aircraft safety specialist commented that it was "almost unheard of" for an powerplant to separate in flight.
He referenced the 1979 American Airlines Flight 191 tragedy, in which 273 individuals were fatally injured after the plane's engine detached as it took off from Chicago's major airport. Engine components had been compromised when it was installed on the aircraft, but the expert said it was premature to determine whether a comparable issue led to the powerplant separation on the MD-11.
The specialist explained the cargo plane would have been able to fly with only two powerplants but the destruction resulting from the wing blaze was likely so great it resulted in the plane's third engine to fail to produce power.
"Given the severe nature of the incident we cannot determine what other damage was caused when the engine came adrift," the expert commented.
A different aircraft specialist said the video evidence appeared to show the third engine had been damaged because it expelled a burst of smoke. The issue could have happened while it was pelted with debris from the fire and the engine detaching.
"The upper engine that released smoke seems to shut down right after," the specialist stated. "That left only the starboard powerplant producing thrust, resulting in a severe power imbalance and making the plane incapable to achieve altitude.
"Losing two engines while departing leaves the aircraft with only a fraction of its thrust and minimal opportunity of maintaining flight, especially at full departure mass," the expert continued.
Reasons for extensive destruction
Post-accident videos revealed a situation of total disorder with multiple fires blazing across a extensive area of the location and smoke billowing into the sky.
The aircraft, which was 34 years old and had been used as a passenger plane before conversion, had previously made one round trip from Louisville to Baltimore in Maryland on the same day.
Authorities haven't verified what cargo was aboard the flight bound for Hawaii, though authorities said the plane was not carrying anything that would create a heightened risk of environmental hazard.
"This involved extended freight transport from Louisville to Honolulu, so the MD-11 was carrying a lot of jet fuel," a specialist said. "That heavy fuel load not only diminished capability but also explains the large fireball observed post-accident."
Authorities informed media that the plane was transporting 144,000 litres of fuel for the long journey when it crashed. The fire was likely amplified on the surface because the plane crashed into a fuel recycling business next to the airport.
A specialist said investigators will now focus on how the initial fire began, and "if wreckage hit the central powerplant, and if previous repairs on the portside powerplant played a role." He added: "Weather conditions were calm and clear, so environmental factors are unlikely."
The federal investigation agency has dispatched personnel to the site and will now lead the probe into the accident's origins, though this can take up to two years to complete.
