An Air India plane crashed while landing at a notoriously tricky airport — here's why 'tabletop' runways can be so treacherous

• An Air India Express plane carrying 190 people crashed on Friday while landing at Calicut International Airport in India.
• The plane overshot the runway, then fell 30 feet into a valley.
• Calicut Airport has what's called a "tabletop runway," which sits at the top of a hill, plateau, or mountain, with steep drop-offs at either end.

An Air India Express flight crashed in Calicut, India on Friday, overshooting the runway while landing. At least 16 people have died, including both pilots. and 123 are injured.

The plane, a Boeing 737-800, continued off the end of the runway and fell down 30 feet into a valley, breaking into two pieces.

The flight, operating as Air India Express Flight 1344, was coming from Dubai in the United Arab Emirates. The flight was part of the Vande Bharat mission to repatriate Indian residents stranded abroad by the COVID-19 pandemic. The 190 people aboard included 174 passengers — 10 of them infants — and six crew members.

Calicut International Airport, located in Kerala, India, is a famously tricky airport for pilots.

The airport's single runway is what's known as a "tabletop runway," the sort built atop a hill, plateau, or mountain, with steep drop-offs past both ends. These leave little margin for error and severely penalize mistakes. Moreover, they can create an optical illusion for pilots, appearing to continue on and on despite giving way to the cliff.

The runway at Calicut, 10/28 — like all airport runways, it is named for the compass direction it faces, and can facilitate takeoffs and landings in either direction depending on winds — is 9,300 feet long, with fall-offs at both ends.

While that is typically long enough to manage larger aircraft including wide-body Boeing 747 and 777 jets, the reduced margin for error, combined with poor visibility conditions, can be hazardous even for smaller planes like the 737.

Friday's crash occurred at about 7:45 p.m. local time, in dark conditions during heavy rain, according to Cirium, a civil aviation database. Tracking data indicated that Friday's flight attempted to land once but aborted the approach at the last minute, went around for a second attempt, then crashed.

A similar crash occurred at Mangalore International Airport in India — another tabletop runway — in May 2010. That case involved a Boeing 737-800 operated from Dubai by Air India Express, which overshot the runway while landing and fell down a hill, bursting into flames. Of 166 passengers and crew aboard Flight 812, 158 were killed.