The news was tragic late on Tuesday night: Singapore Airlines flight SQ321 had hit turbulence en route from London to Singapore, resulting in one fatality and up to 71 injuries, some of them serious.

In my near four decades of flying that exact route as a Qantas captain, I learnt there are particular challenges pilots face, especially at this time of year. It appears the Boeing 777-300ER aircraft in question struck severe turbulence entering the notorious Bay of Bengal, between the subcontinent of India and the Malaysian Peninsula.

This time of year, the Inter-tropic Convergence Zone, or ITZ, is very active. That’s a fancy aviation name for the monsoon, which we know simply as the “wet season” in northern Australia. Those ancient trade winds, which our international travelling forebears used to sail around the world, collide somewhere close to the equator. That collision line is the ITZ, and it moves north or south of the equator depending on the season.

When they meet, those opposing trade winds have to go somewhere, creating instability in the atmosphere that can translate into severe weather and turbulence, and a bumpy ride if you’re flying near them.

Current weather charts show a significant cloud mass right across the bay, with embedded thunderstorms up to 55,000 feet. Unless you’re flying the old........

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