Were the unfortunate 50 or so passengers injured onboard Monday’s LATAM Airways flight LA800 from Sydney to Auckland wearing their seatbelts? We have been conditioned to put our seatbelts on, and keep them on, whenever we get into a car, so why not put them on and keep them on when flying in a plane?

We’re told to fasten our seatbelts during pre-flight safety demonstrations, during landing and take-off, but once that much-anticipated ping is heard after climb-out and the seatbelt sign disappears – particularly on long flights – you soon hear the familiar click-clack as many passengers decide the rest of the flight will be smooth and remove their pesky restraints. This occurs despite the request from cabin crew and pilots to keep them fastened at all times for safety.

LATAM Airlines flight LA800 dropped dramatically, injuring passengers as a result.

Why should you bother to do that? Let’s consider what flying has become over the past 100-plus years and, more importantly, since the jet age.

I’m old enough to remember when flying was an intrepid adventure. I recall boarding snarling, flame-spitting, piston-engined aircraft. Vibration and turbulence was the norm. In those days, you wouldn’t have dreamt of removing your seatbelt for fear of being flung about the cabin and landing unceremoniously on some strangers lap. Or worse.

But since the advent of aircraft cabin pressurisation and smooth jet engines we have been lulled into a calm tranquillity where the odd bump or upset is unusual. Plus we get used to the pilots warning when turbulence is ahead and the seatbelt sign flashing on, so we think we’ll be warned when we need to buckle up.

Monday’s hell-ride shows that’s not always the case.

Consider your situation: you’ve been herded onto a long aluminium tube with perhaps hundreds of other fellow travellers. That aluminium tube, once established at cruise altitude, is hurtling through the upper atmosphere at speeds exceeding 900km/h. At such velocity, any slight upset can be magnified several times in the cabin, particularly down the back of the plane as the turbulence corkscrews around the fuselage. Think of a dog wagging its tail – the tip of the tail travels a lot more than the other end. An aircraft is designed to wag its tail. The human body, unrestrained by a seatbelt, is not. That’s why they put first class passengers up front, where the ride is smoothest.

This “wagging” and “flapping” is for structural integrity and load relief within the airframe: just look at the wing tips “flapping” about in turbulence. Without that “wagging” and “flapping”, stress would be concentrated somewhere within the aircraft structure. Structural and metal fatigue would result reducing the “life” and strength of the aircraft.