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No fewer than nine individuals lost their lives and 11 left injured following a UPS cargo plane crashed during departure from a major air hub in Kentucky's largest city on Tuesday evening.

Aviation experts believe the plane crashed due to one engine failed and another appeared to be damaged while lifting off.

It is unclear what caused the plane to crash, prompting a huge explosion to erupt after it couldn't become airborne from the airstrip. Video evidence showed fire had already engulfed one wing of the plane while it was attempting to take off, 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 is apparent is that the 144,000 litres of jet fuel on board the trijet aircraft required for the journey 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 distribution hub for its worldwide network and its designated flight was beginning of a 4,300 mile journey to Hawaii's capital when the freight aircraft attempted to take off.

Tracking information from FlightRadar24 indicates the plane started moving along the 17R runway at around 5:15 PM local and managed to reach a top speed of 214mph.

But verified footage shows that by the time the plane achieved this velocity a fire had completely engulfed its port side and the plane couldn't climb before the massive explosion.

Officials issued a local safety directive to area inhabitants and dispatched numerous fire crews to the scene.

The state's governor verified particulars seen in CCTV footage that shows the aircraft flying just feet above the surface before a bright flash consumed the aircraft. It is then observed crashing onto the ground as a huge fireball erupts around it about a minute after departure.

A verified clip recorded by drivers on adjacent roads displayed the fire rising into the air while later videos showed smoke billowing from the scene.

Aerial images shown on local media depicted wreckage scattering across the airstrip and falling onto the tops of multiple nearby establishments.

What could have caused the crash?

Air traffic control communications reviewed are mostly unclear and full of interference so no clear dialogue can be discerned about the crash as it unfolded.

However, experts suggested that a dramatic failure of two of the engines may have been responsible for the disaster.

The trijet cargo aircraft employs 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 fire consuming the left wing of the aircraft, which then tilted to the left as it attempted to gain lift and take-off.

Two experts independently suggested the left engine may have detached from the plane after suffering from a mechanical or structural failure.

Additional photographs captured post-accident showed a charred engine sitting on the turf adjacent to the airstrip.

An experienced former aviator and aviation safety expert said that it was "almost unheard of" for an powerplant to separate during operation.

The expert recalled the 1979 aviation disaster tragedy, in which 273 individuals were killed when the aircraft's powerplant separated as it took off from Chicago's major airport. Engine components had been compromised when it was replaced on the plane, but the specialist said it was premature to determine whether a similar fault caused the powerplant separation on the MD-11.

The expert said the cargo plane would have been capable of flight with just two engines but the destruction resulting from the wing blaze was probably extensive enough it resulted in the aircraft's remaining 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," he said.

A different aircraft specialist observed the video evidence seemed to indicate the remaining powerplant had been compromised because it expelled a burst of smoke. The issue could have happened while it was pelted with debris from the fire and the powerplant separation.

"The upper engine that released smoke appears to wind down right after," the specialist said. "That left only the starboard powerplant producing thrust, creating a significant thrust asymmetry and leaving the aircraft unable to achieve altitude.

"Losing two engines while departing results in only a third of its power and minimal opportunity of staying airborne, especially at maximum take-off weight," the specialist continued.

Reasons for extensive destruction

Post-accident videos showed a scene of complete chaos with numerous blazes blazing across a large swathe of the location and smoke rising upward.

The aircraft, which was three decades old and had been used as a passenger plane before conversion, had already completed one round trip from the Kentucky hub to Baltimore in Maryland on the same day.

Authorities haven't verified which goods was aboard the flight bound for Hawaii, though officials said the aircraft didn't contain anything that would pose an increased danger of contamination.

"This involved extended freight transport from Louisville to Honolulu, so the MD-11 was transporting a significant fuel quantity," an expert commented. "That heavy fuel load not only reduced performance but also accounts for the large fireball observed post-accident."

Authorities told reporters 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 aircraft slammed into a fuel processing facility adjacent to the airfield.

A specialist said authorities will concentrate on the origin of the blaze, and "whether debris struck the central powerplant, and if previous repairs on the left engine played a role." He added: "Atmospheric conditions were favorable, so weather-related causes are unlikely."

The National Transportation Safety Board has sent a team to the site and will take charge of the investigation into the causes of the crash, though this can take up to two years to finalize.