How this Kentucky UPS Aircraft Crash Developed and What Could Have Led to It

At least nine individuals have died and 11 others were hurt after a freight aircraft crashed during departure from an international airport in Kentucky's largest city on Tuesday evening.

Aviation experts suggest the aircraft went down due to 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 huge explosion to erupt after it couldn't become airborne from the runway. Video evidence revealed flames were consuming a single wing of the aircraft while it was attempting to take off, potentially spreading across the aircraft and triggered the blast, or the jet could have caught fire upon hitting ground-based obstacles.

What's clear is that the 38,000 gallons of fuel on board the MD-11 jet needed for the flight likely escalated the fire, which quickly spread to several buildings beyond the runway and continued burning for hours.

How did it start?

UPS uses Louisville Muhammad Ali International Airport as a distribution hub for its global operations and its Flight 2976 was at the start of a 6,920 kilometer trip to Honolulu in Hawaii when the cargo plane attempted to take off.

Data from flight monitoring services indicates the plane started moving along the 17R runway at around 17:15 local time 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 aircraft failed to gain altitude before the massive explosion.

Authorities activated a local safety directive to local residents and scrambled numerous fire crews to the location.

The state's governor confirmed details seen in CCTV footage that depict the aircraft flying just metres off the ground before a intense light consumed the aircraft. It is then observed crashing onto the terrain as a massive fire explosion erupts around it about a minute into its journey.

Authenticated footage recorded by drivers on adjacent roads displayed the fire rising into the air while subsequent recordings revealed smoke pouring from the area.

Overhead photographs broadcast by regional news outlets showed debris showering the runway and falling onto the roofs of at least two local businesses.

Potential causes of the accident

Air traffic control communications reviewed are mostly unclear and filled with static so no meaningful conversation can be discerned about the crash as it developed.

However, experts proposed that a catastrophic malfunction of multiple engines may have been responsible for the disaster.

The trijet cargo aircraft uses three powerplants. Two are installed under the airfoils, and a third is positioned in the rear section at the base of the vertical stabilizer.

Footage confirmed revealed a blaze engulfing the port wing of the aircraft, which then tilted to the left as it attempted to gain lift and take-off.

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

Separate images captured post-accident showed a burned powerplant resting on the grass next to the runway.

A retired airline pilot and aviation safety expert commented that it was "almost unheard of" for an engine to detach during operation.

He referenced the 1979 American Airlines Flight 191 tragedy, in which 273 individuals were killed when the plane's engine detached as it departed from O'Hare International Airport. Engine components had been compromised when it was replaced on the plane, but the expert said it was too early to say whether a similar fault caused the engine to detach 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 aircraft's remaining engine to lose thrust.

"Given the severe nature of the incident we cannot know additional destruction was caused when the powerplant separated," the expert commented.

A different aircraft specialist observed the video evidence appeared to show the remaining powerplant had been damaged because it expelled a burst of smoke. The issue could have occurred while it was struck by wreckage from the blaze and the powerplant separation.

"The tail-mounted powerplant that released smoke seems to shut down right after," the expert stated. "This left just the starboard powerplant producing thrust, creating a significant thrust asymmetry and leaving the aircraft unable to gain height.

"Failing two powerplants during take-off leaves the aircraft with only a third of its power and minimal opportunity of maintaining flight, especially at full departure mass," the expert added.

Why did the crash cause such damage?

Post-accident videos showed a situation of total disorder with multiple fires burning across a large swathe of the site and smoke rising upward.

The plane, which was 34 years old and had been used as a passenger plane until 2006, had already completed one round trip from Louisville to the East Coast on the same day.

It has not been confirmed which goods 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 was a long-haul cargo flight from Louisville to Honolulu, so the MD-11 was carrying a lot of jet fuel," an expert said. "The substantial fuel quantity not only diminished capability but also explains the massive explosion observed post-accident."

Officials told reporters that the plane was transporting 144,000 litres of jet 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.

The expert said investigators will now focus on the origin of the blaze, and "if wreckage hit the centre engine, and whether earlier maintenance on the left engine were a factor." The expert continued: "Weather conditions were calm and clear, so environmental factors are improbable."

The federal investigation agency has sent a team to the site and will take charge of the probe into the causes of the crash, though such inquiries may require years to finalize.