Check It Airlines 3921 was an international flight operated by Check It Airlines from Hip City International Airport, Hip City, Check It Republic, to Baoji International Airport, Baoji City, South Baoji. On 15 January 2012, the Roeing 737-300 violently exploded while waiting on runway, killing 16 Robloxians and injuring 41 more. This would become the airline's third hull loss, but it would be the 737-300's only hull loss during 2012. However, this was not the first explosion-related accident for the Roeing 737 Classic, as other accidents have happened beforehand.
Aircraft
The aircraft was a 21-year old Roeing 737-3S1. It had its first flight on March 18, 1990, and was delivered to the El Bloxalvadoran airline TACB on 5 Febuary 1991. It was powered by two CFM International CFM56-3B2 engines. The airliner was abandoned when TACB dropped their 737-300s in 1999, and the airliner was eventually refurbished then given to Check It Airlines around 2007. The airplane never had any fuel inerting systems installed whatsoever.
Accident
The mostly stripped-down plane around 2016.
The plane left the gate around 1:04 PM, most of the process taxiing and waiting on taxiways. Around 1:07, the plane was able to hold short on the runway, and was given clearance to taxi 1 minute later. The plane, at the time was waiting for takeoff to steer clear of wake turbulence from other planes, when at 1:08, a massive explosion ripped out from both from the cabin floor and the bottom of the wingbox. Multiple seats were thrown out of the airplane, killing those victims while others were experienced burns or smoke inhalation according to medical treatments. All 3 crew members including the 2 pilots survived except for 1 flight attendant. The rear fuselage bent due to the lack of upper structural support. The aircraft was declared as a fatal hull loss, with the plane being parked as use as a firefighting training aircraft until 2017.
Investigation
As the Check It Republic lacked any transportation safety body, so it was handled by Bloxstralia, one of the country's neighbors with a transportation safety body which had one known as the Bloxstralian Safety Transportation Bureau (BTSB).
The BTSB could not find any plausible causes for the accident, but some have been suggested that the explosion could have been caused by sparks, but what made the sparks is unknown, but 3 contenders have been chosen:
- Activated fuel pump with the presence of metal shavings, like Thai Airways 114.
- Damaged/Defective wiring, like in Ro-Philippines 143.
- Short circuiting.
The central fuel tank was 3/4ths full, so it could be jam-packed for the flight, and it was suggested that there were leftover fuel vapors, giving it more plausible causes. Today, the real cause is unknown and hasn't been discovered despite hull inspection.