The science of flying and how humidity, heat pose challenges

The moments after Air India flight 171 took off from Ahmedabad airport at 40 seconds past 1.38 pm were routine for any flight: A massive Boeing 787 Dreamliner barrels down runway 05/23, its nose is pointed skyward in the classic climbing posture.

- Binayak Dasgupta

NEW DELHI: Soon, its nosewheels raise off the ground, followed by the pair of heavier rear landing gears and the hulking wide body jet is now aloft by the physics of aerodynamics.

But soon, that begins to change: instead of gaining altitude, it begins sinking. For 33 seconds, the aircraft maintains this contradictory orientation—nose up, yet descending—before disappearing behind trees and erupting into flames.

This haunting video captures a fundamental breakdown in the physics that governs all flight: the delicate equilibrium of forces—of thrust, that propels the jet forward to overcome drag so that the giant wings generate lift enough to overcome weight.

The root cause for why this breakdown occurred is now the subject of a multi-agency, multicountry investigation led by India's Aircraft Accident Investigation Bureau (AAIB), with Air India, plane-maker Boeing and engine manufacturer GE Aerospace helping uncover technical clues and with assistance from air crash investigators from the UK and US.

Experts analysing the video—which will now be a crucial part of the investigation—were struck by how the plane was doomed at a stage of flight where the laws of physics are simple, as opposed to being done in by a more dramatic outcome, such as being knocked off its path by a strong gust of wind or incurring what is known as a tail strike when pilots take off too aggressively. Understanding these forces becomes crucial as investigators determine whether engine failure, miscalculation of weights, environmental factors—or, in fact, a combination of any of these played a role.