No fewer than nine people have died and 11 others were hurt after a freight aircraft went down during departure from a major air hub in Louisville, Kentucky on Tuesday evening.
Aircraft specialists suggest the aircraft went down due to one engine failed 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 runway. Video evidence revealed flames were consuming a single wing of the plane during its takeoff attempt, which may have spread across the aircraft and caused the explosion, or the plane might have ignited after colliding with an object on the ground.
What's clear is that the 144,000 litres of jet fuel on board the MD-11 jet needed for the flight probably intensified the fire, which quickly spread to multiple structures beyond the runway and burned for hours.
How did it start?
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 Hawaii's capital when the freight aircraft attempted to take off.
Data from flight monitoring services indicates the plane began to taxi along the designated runway at around 5:15 PM local and managed to reach a maximum velocity of 344km/h.
However, confirmed videos demonstrate that by the time the plane achieved this velocity a blaze had fully consumed its left wing and the plane couldn't climb before the massive explosion.
Authorities activated a shelter-in-place order to area inhabitants and dispatched numerous fire crews to the scene.
Governor Andy Beshear verified details seen in CCTV footage that depict the aircraft flying just metres off the ground before a bright flash engulfed the plane. It is then seen slamming into the ground as a huge fireball erupts around it about a minute after departure.
Authenticated footage taken by motorists on a nearby highway showed the flames erupting into the skyline while later videos showed smoke pouring from the area.
Aerial images shown on local media showed debris showering the runway and falling onto the roofs of multiple nearby establishments.
What could have caused the crash?
Air traffic control communications reviewed are mostly unclear and filled with static so no meaningful conversation can be discerned about the incident as it developed.
But analysts suggested that a dramatic failure of multiple engines may have been the cause of the tragedy.
The trijet cargo aircraft employs three engines. Two are mounted under the airfoils, and a third is built into the rear section at the base of the vertical stabilizer.
Video verified revealed a blaze engulfing the port wing of the aircraft, which then leaned leftward as it tried to achieve altitude and become airborne.
Multiple specialists independently suggested the portside engine may have separated from the plane after suffering from a technical or physical breakdown.
Additional photographs captured post-accident showed a burned powerplant sitting on the turf adjacent to the airstrip.
An experienced former aviator 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 killed 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 said it was premature to determine whether a comparable issue led to the powerplant separation on the trijet.
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 probably extensive enough it resulted in the plane's third engine to lose thrust.
"Given the severe nature of the incident we cannot determine additional destruction was done when the powerplant separated," the expert commented.
A different aircraft specialist observed the footage seemed to indicate the third engine had been compromised because it released smoke. The issue could have occurred while it was pelted with debris from the fire and the powerplant separation.
"The tail-mounted powerplant that released smoke appears to wind down right after," the specialist stated. "That left only the right engine generating power, resulting in a significant thrust asymmetry and making the plane incapable to achieve altitude.
"Losing two engines during take-off leaves the aircraft with only a fraction of its thrust and little chance of staying airborne, especially at maximum take-off weight," the specialist added.
Why did the crash cause such damage?
Footage from the aftermath showed a scene of complete chaos with multiple fires blazing across a large swathe of the location and smoke billowing into the sky.
The plane, which was three decades 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 Tuesday.
Authorities haven't verified what cargo was aboard the flight bound for Hawaii, though officials stated the aircraft didn't contain anything that would create a heightened risk of environmental hazard.
"This involved extended freight transport from Kentucky to Hawaii, so the MD-11 was carrying a significant fuel quantity," an expert said. "That heavy fuel load not only diminished capability but also explains the large fireball seen after the crash."
Authorities informed media that the aircraft was transporting 144,000 litres of fuel for the extended trip when it went down. The fire was probably intensified on the ground because the plane crashed into a fuel processing facility next to the airport.
A specialist indicated investigators will now focus on the origin of the blaze, and "whether debris struck the centre engine, and whether earlier maintenance on the left engine played a role." The expert continued: "Weather conditions were calm and clear, so weather-related causes are unlikely."
The federal investigation agency has dispatched personnel to the site and will take charge of the probe into the accident's origins, though this can take up to two years to complete.
