MUMBAI: The Air India Express crash on Friday has, once again brought to fore, the subject of tricky tabletop runways and whether enough has been done in India to ensure safe landings on them.A Vande Bharat flight IX1344 from Dubai to Kozhikode, skidded off the runway at the destination airport on Friday night and fell into a 30 feet deep ditch, killing 18 people including the two pilots. Almost a 100 people, including the cabin crew, were seriously injured.A tabletop runway, like the one in Kozhikode, is built on the plateau of a hill, with one or both ends leading to a deep gorge. The runways are tricky and can create an optical illusion which makes it difficult for a pilot to land safely.India has such runways in three airports: Mangalore where the last crash, also of an Air India Express flight, happened, and Lengpui airport in Mizoram, apart from Kozhikode.The incident has brought to light, several questions and recommendations raised and given after the Mangalore air crash in May 2010. The flight IX812 coming in from Dubai skidded of the runway in full force, fell downhill and burst into flames, killing 158 people on board.Mohan Ranganathan, an aviation expert and former member of the Civil Aviation Safety Advisory Council had in 2011 written to the aviation regulator the Directorate General of Civil Aviation (DGCA), about the absence of a minimum, runway safety area (RESA) around the Kozhikode airport runway. RESA is an area surrounding the runway to prevent maximum damage in case a plane undershoots, overshoots or skids off it.In his letter, which Ranganathan tweeted on Saturday, he said the runway didn’t have the minimum RESA on one end and no RESA on the other.A senior official at the Airports Authority of India said the minimum RESA was built. But experts differ.The runway length at Kozhikode is 9,831 feet, according to online aeronautical chart collector Sky Vector. It reached this length after at least two extensions. NITI Aayog CEO Amitabh Kant Friday tweeted he had it extended from 4,500 feet to 6,000 feet in his tenure as district collector.“9,831 feet is adequate length, but there isn’t enough safety area on both ends. Assuming the aircraft landed within a safe 3,000 feet, the speed was higher than normal, the downslope, and the slippery surface you would have the extend the calculation of the safety area in your head. The absence of adequate safety area would aggravate the problem,” said Shakti Lumba, an aviation veteran, who has flown with Indian Airlines (Air India’s former domestic arm) and IndiGo.Ranganathan in his tweet, presented an old obstacle chart of the Kozhikode runway, which showed a steep downward slope after a third of the runway. Also, whenever an aircraft lands, it spurts out a gush of rubber which collects on the runway. The rubber, mixed with rain water makes the surface more slippery, said Lumba.Rain played a key role in differentiating this crash from the last one in Mangalore said a former senior Air India executive who had played a key role in investigating the first crash."In the Mangalore crash, the weather wasn't a factor at all. The pilot touched down late, then understood he couldn't control the plane. But he increased the power of the aircraft and attempted a go around. He went and crashed with full power and the aircraft burst in flames," said Raghu Kumar, former executive director of Air India."In this (Kozhikode) case too, the pilot touched down late, but here weather was a key negative factor," added Kumar who led the search for the cockpit voice recorder and black box after the Mangalore air crash.In a statement on Friday, Air India said the Aircraft Accident Investigation Bureau, the DGCA and flight safety departments have reached the venue and are investigating the incident.