These flight routes suffer the world's worst turbulence

The deadly turbulence on a Singapore Airlines Ltd. flight on its way from London to Singapore has put a spotlight on the world's most unstable air routes.

A British man was killed and seven other people were critically injured after Singapore Air flight SQ321 encountered severe turbulence as it entered Thai airspace Tuesday, triggering an emergency landing in Bangkok.

While the most turbulent flights of all connect Santiago in Chile to Santa Cruz in Bolivia, there are similarly bumpy rides across the world, according to the turbli database. Flights leaving Tokyo dominate the list of the roughest long-haul services.

Strong turbulence is produced when air streams traveling at significantly different speeds come together. This is typically encountered at the boundaries of jet streams, over mountains and in certain cloud storms, according to the turbli website.

For instance, turbulence on the Santiago-Santa Cruz route is generated by winds from the Pacific Ocean to the Atlantic Ocean flowing almost perpendicular to the Andes. The equator is also a well-known region for turbulence because of strong upward currents and thunderstorm activity, turbli said. Japan has high levels of mountain- and ocean-induced turbulence.

The turbli website produced its rankings by analyzing 150,000 routes using data from UK and US government meteorological agencies.