At least nine people have died and 11 others were hurt after a freight aircraft crashed while taking off from a major air hub in Louisville, Kentucky on Tuesday evening.
Aviation experts suggest the plane crashed after a single engine malfunctioned and another appeared to be damaged during take-off.
The exact cause remains unknown what caused the plane to crash, prompting a massive fireball to erupt after it failed to take-off from the airstrip. Video evidence showed fire had already engulfed a single wing of the aircraft while it was attempting to take off, which may have spread through the plane and caused the explosion, or the plane might have ignited upon hitting ground-based obstacles.
What's clear is that the 38,000 gallons of fuel aboard the trijet aircraft required for the journey likely escalated the blaze, which rapidly extended to several buildings past the airstrip and burned for hours.
What initiated the incident?
UPS operates from Louisville Muhammad Ali International Airport as a distribution hub for its global operations and its Flight 2976 was beginning of a 4,300 mile journey to Hawaii's capital when the freight aircraft attempted to take off.
Data from FlightRadar24 shows the plane started moving along the designated runway at around 5:15 PM local and attained a top speed of 344km/h.
But verified footage demonstrate that when 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 issued a shelter-in-place order to area inhabitants and dispatched hundreds of firefighters to the scene.
Governor Andy Beshear confirmed details visible in security camera recordings that depict the plane traveling just metres off the ground before a bright flash consumed the aircraft. It is then seen slamming into the terrain as a huge fireball erupts around it about a minute after departure.
Authenticated footage recorded by motorists on a nearby highway displayed the flames erupting into the skyline while later videos showed 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?
ATC transmissions examined are mostly unclear and full of interference so no clear dialogue can be discerned about the crash as it developed.
However, experts proposed that a dramatic failure of multiple engines may have been responsible for the disaster.
The trijet cargo aircraft uses three powerplants. Two are mounted under the wings, 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 aircraft, which then tilted to the left as it tried to achieve altitude and take-off.
Multiple specialists separately proposed the left engine may have detached from the plane after suffering from a mechanical or structural failure.
Additional photographs taken after the crash displayed a burned powerplant sitting on the turf next to the runway.
A retired airline pilot and aviation safety expert commented that it was "almost unheard of" for an powerplant to separate during operation.
The expert recalled the 1979 American Airlines Flight 191 disaster, in which 273 people were fatally injured when the aircraft's powerplant separated as it took off from Chicago's major airport. Parts of the engine had been damaged when it was installed on the aircraft, but the expert stated it was too early to say whether a similar fault caused the engine to detach on the MD-11.
The specialist explained the freight aircraft would have been capable of flight with just two engines but the destruction resulting from the fire on the left wing was probably extensive enough it resulted in the plane's third engine to fail to produce power.
"Given the severe nature of the incident we cannot determine additional destruction was done when the engine came adrift," the expert commented.
Another aviation expert observed the video evidence seemed to indicate the remaining powerplant had been compromised because it expelled a burst of smoke. The damage could have occurred while it was pelted with debris from the blaze and the engine detaching.
"The tail-mounted powerplant that released smoke appears to wind down right after," the specialist stated. "This left just the right engine producing thrust, creating a significant thrust asymmetry and making the plane incapable to achieve altitude.
"Failing two powerplants while departing leaves the aircraft with only a fraction of its thrust and minimal opportunity of maintaining flight, particularly under maximum take-off weight," the specialist added.
Why did the crash cause such damage?
Footage from the aftermath revealed a situation of total disorder with multiple fires burning across a extensive area of the location and smoke rising upward.
The plane, which was three decades old and had been used as a passenger plane before conversion, had previously made one round trip from Louisville to the East Coast on the same day.
It has not been confirmed what cargo was on board the Hawaii-bound aircraft, though authorities stated 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 trijet was transporting a significant fuel quantity," an expert said. "That heavy fuel load not only diminished capability but also accounts for the massive explosion seen after the crash."
Officials told reporters that the aircraft was transporting 144,000 litres of jet fuel for the long journey when it went down. The fire was likely amplified on the ground 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 centre engine, and if previous repairs on the left engine were a factor." The expert continued: "Weather conditions were calm and clear, so environmental factors are unlikely."
The National Transportation Safety Board has dispatched personnel to the location and will now lead the probe into the accident's origins, though this can take up to two years to finalize.
