ACT is a Turkish airline flying freight using Boeing 747’s. The 747 is huge inside and can hold tons of freight. Planes sliding off runways is something that seldom happens, but it does happen. Reasons are; poor runway conditions, poor weather conditions, poor tires on the landing gears, poor training with landing and keeping the plane on the centerline. I have also seen this happen when the plane lands too fast or the pilot didn’t set the autobraking system.
I have been to Hong Kong back in 1971 when they had the old airport (Kai Tak). I was there on business at the time when I worked for DuPont and before I began flying. The old airport was located on the Kowloon peninsula and was old with safety issues. The pilots that flew into the old airport told me there were times when they had to fly between buildings to get to the runway. Good Grief! Almost as bad as landing at San Diego.
According to the article from the BBC, the four crew members were all safe, but the two workers in the truck were riding behind a fence that ran a safe distance from the runway, but the plane went through the fence striking the truck with the two occupants inside and pushed it into the South China Sea. I remember speaking with an engineer while in HK and he had told me that every day billions of dollars flow through the city in cash, diamonds and gold.