Why did the Air India rescue flight not take a straight route over the Himalayas to Magadan?

Air India flight AI173, travelling from Delhi to San Francisco, made an emergency landing in Magadan, Russia, due to a technical issue on June 6. A ferry flight (Boeing 777) was subsequently flown from Mumbai to Magadan to transport the passengers and crew to San Francisco.

The ferry flight, with callsign AI 173D, has now safely arrived at its destination (June 8).

The route taken

• The ferry flight AIC 173D left Mumbai and flew north towards Pakistan. Avoiding Afghanistan in the west, it made its way over Tajikistan, Kyrgyzstan and Kazakhstan before curving eastwards over Russia to land at the Sokol Airport in Magadan, Russia.

• This route clearly looked to avoid a straighter route over the Himalayas, Tibetan Plateau, then on to China and Mongolia, to terminate at the airport in Magadan.

Ever wondered why?

• Flying over the vast Himalayas whose average elevation is more than 20,000 feet above sea level, has its own set of challenges.
• The Boeing 777 (the jetliner sent to ferry) has a comfortable cruise ceiling of around 35,000 feet, coinciding with the lower stratosphere, where oxygen is scarce. But the aircraft won't climb that high to avoid lowering the altitude while maintaining a distance from the mountains below, in case of lack of oxygen in the cabin.

• The lack of oxygen causes cases of hypoxia in passengers, putting their lives at risk mid-air.
• In case the cabin pressure drops, at higher altitudes the oxygen masks pop out overhead. The supply of oxygen through the masks is, however, limited. This adds to more risks and uncertainties.
• And such a manoeuvre up in the air, making the airliner drop by several thousand feet in a few minutes, isn't enough and also could cause turbulence; putting passengers' lives in danger.
• Low oxygen at high altitudes often causes turbulence because of the presence of high winds.
• Also, in cases of emergency, there aren't many airports/airstrips or flat surfaces around to land amidst the Himalayas.
• Apart from the threats to lives onboard; at 20,000 feet the temperature outside could go as low as -25 degrees Celsius. There's a slight chance that the jet fuel in the tank could freeze.

ALSO READ: How a revised Air India route helped AI 173 land on ground in Magadan

What is hypoxia?

• Hypoxia refers to a medical condition where tissues do not receive a sufficient supply of oxygen at the cellular level, leading to an imbalance in homeostasis (an ideal state where the body functions function correctly).
• This situation can arise from insufficient delivery of oxygen to the tissues, either due to reduced blood flow or oxygen levels in the bloodstream.

Not just the Air India ferry flight AI 173D, airplanes in general avoid the Himalayas, no matter how short the route might be. The Himalayas, in addition to posing all the above-mentioned challenges, also comes with extremely unpredictable weather. This in turn makes an emergency landing on the Himalayas impossible.

Except for, say, a country like Nepal which is nestled completely in the Himalayas, air carriers avoid the mountains.