No fewer than nine people have died and 11 left injured following a UPS cargo plane crashed during departure from a major air hub in Louisville, Kentucky on Tuesday evening.
Aviation experts believe the plane crashed after a single engine malfunctioned and another appeared to be damaged while lifting off.
The exact cause remains unknown what caused the plane to crash, prompting a massive fireball to erupt after it couldn't become airborne from the airstrip. Footage showed flames were consuming one wing of the plane during its takeoff attempt, which may have spread across the aircraft and caused the explosion, or the jet could have caught fire after colliding with an object on the ground.
What's clear is that the 144,000 litres of fuel aboard the MD-11 jet required for the journey likely escalated the blaze, which quickly spread to several buildings beyond the runway and burned for hours.
What initiated the incident?
The shipping giant operates from the Louisville air hub as a logistics center for its global operations and its designated flight was at the start of a 4,300 mile trip to Honolulu in Hawaii when the cargo plane initiated departure.
Data from FlightRadar24 indicates the plane started moving along the designated runway at around 17:15 local time and managed to reach a top speed of 214mph.
However, confirmed videos demonstrate that by the time the plane achieved this velocity a blaze had fully consumed its left wing and the aircraft failed to gain altitude before the massive explosion.
Authorities activated a local safety directive to area inhabitants and dispatched hundreds of firefighters to the location.
Governor Andy Beshear verified details seen in CCTV footage that depict the plane traveling just metres off the ground before a bright flash consumed the aircraft. It is then observed crashing onto the ground as a huge fireball ignites surrounding it about a minute into its journey.
A verified clip recorded by drivers on adjacent roads showed the fire rising into the air while later videos revealed smoke billowing from the scene.
Aerial images shown on local media depicted debris showering the runway and falling onto the roofs of multiple nearby establishments.
Potential causes of the accident
ATC transmissions reviewed are largely garbled and full of interference so no clear dialogue can be heard about the crash as it unfolded.
However, experts suggested that a catastrophic malfunction of two of the engines may have been responsible for the disaster.
The MD-11 transport plane employs three powerplants. Two are installed under the airfoils, and a third is built into the tail at the bottom of the tail fin.
Video verified showed a blaze engulfing the left wing of the aircraft, which then tilted to the left as it tried to achieve altitude and take-off.
Two experts independently suggested the left engine may have separated from the plane following a technical or physical breakdown.
Separate images captured post-accident displayed a charred engine sitting on the grass 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.
The expert recalled the 1979 American Airlines Flight 191 tragedy, in which 273 people were fatally injured when the plane's engine detached as it departed from O'Hare International Airport. Engine components had been damaged when it was replaced on the plane, but the expert said it was premature to determine whether a comparable issue caused the powerplant separation on the MD-11.
The expert explained the cargo plane would have been able to fly with only two powerplants but the destruction resulting from the wing blaze was probably extensive enough it caused the plane's third engine to lose thrust.
"With such a catastrophic event we cannot know what other damage was done when the engine came adrift," he said.
A different aircraft specialist observed the footage seemed to indicate the third engine had been damaged because it expelled a burst of smoke. The damage could have occurred while it was struck by wreckage from the fire and the powerplant separation.
"The upper engine that expelled a puff of smoke seems to shut down almost immediately afterwards," the expert said. "That left only the starboard powerplant generating power, resulting in a significant thrust asymmetry and leaving the aircraft unable to achieve altitude.
"Losing two engines during take-off leaves the aircraft with only a third of its power and little chance of staying airborne, especially at full departure mass," the specialist added.
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 operated for passenger travel before conversion, had previously made one round trip from the Kentucky hub to Baltimore in Maryland on the same day.
It has not been confirmed what cargo was aboard the Hawaii-bound aircraft, though authorities said the aircraft didn't contain 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 significant fuel quantity," an expert said. "That heavy fuel load not only reduced performance but also accounts for the large fireball seen after the crash."
Officials informed media that the plane was transporting 38,000 gallons of fuel for the extended trip when it went down. The fire was probably intensified on the surface because the plane crashed into a fuel recycling business adjacent to the airfield.
A specialist indicated investigators will now focus on how the initial fire began, and "whether debris struck the centre engine, and whether earlier maintenance on the portside powerplant were a factor." The expert continued: "Atmospheric conditions were favorable, so weather-related causes are improbable."
The National Transportation Safety Board has sent a team to the location and will now lead the probe into the accident's origins, though this can take up to two years to finalize.
