Captain Sumeet Sabharwal and his first officer were in charge of an aircraft that was refusing to climb after their Boeing 787 took off at Ahmedabad airport in India.

Video of the take-off showed the airliner halting its climb and beginning to sink seconds after pulling away from runway 23. The pilots made a mayday call to controllers, alerting them to a distress situation, about 60 seconds after starting their take-off roll.

Pilots trying to understand the events that led the 787-8 series airliner to lose lift and struggle to stay airborne, before slamming into a building, considered a loss of engine thrust as a possible cause.

Some pilots reviewing the data believed the aircraft may have suffered a drop in engine power, a line that was circulating in Indian media. A government proposal to ground all Indian Boeing 787s could suggest a technical failure of this nature.

Other pilots focused more on a visible anomaly: the abnormal configuration of the wing flaps and landing gear. Some veteran pilots speculated that the take-off flaps had been retracted by mistake.• British couple were on flight 171, family says The 787 Dreamliner, Boeing’s flagship plane, has been in airline service since 2011 and is packed with safety systems. It can, like all airliners, climb away even if a single engine fails. It will sound multiple alarms if pilots attempt to start their take-off roll down the runway without setting the wing flaps and slats that increase lift.Video of the nose dropping from the climb angle and the aircraft wallowing at about 400 feet over the ground suggested that it may not have been under full power, experts said. More glaringly the footage indicates that the flaps were fully or partially retracted. That would have deprived the airliner of the lift crucial for avoiding an aerodynamic stall that it experienced seconds later when the pilot pulled the nose up in a desperate final attempt to stay airborne.The Boeing 787’s tail came to rest on a buildingCENTRAL INDUSTRIAL SECURITY FORCE /AFP/GETTY IMAGESThe cause of the crash will not be determined until the black box recorders have been found and downloadedAMIT DAVE/REUTERSThe aircraft was flying at 174 knots over the ground in its last data transmission, which would have been just over its stalling speed of 140-160 knots without flaps, according to Boeing data.Landing gear is normally retracted on the order of the pilot flying just after take-off, as soon as the non-flying pilot calls out “positive climb”. This reduces the substantial drag from the air caused by the multiple wheels and enables the aircraft to climb much better. Initially the Air India Boeing did climb at a normal angle, according to flight data and professional pilots who studied the video, yet it kept its wheels down.• Flight 171 crash is worst aviation disaster for Britain since 9/11Some pilots suggested that the non-flying pilot could have accidentally retracted the flaps. “I think the co-pilot grabbed the flap handle and raised the flaps instead of the gear,” Steve Scheibner, an American Airlines captain, said. “If that happened this explains a lot about why this airplane stopped flying, why the lift over the wings died,” he added on his well-regarded aviation channel. “The flight characteristics look to me like the only way that could have happened is that they didn’t have the proper flap setting,” Scheibner, a former US Navy aviator who flies long haul on the larger Boeing 777, added.• How the Air India crash unfoldedDenys Davydov, a Boeing 737 captain with a Ukrainian airline, said: “It looks like the flaps were up and the gear was down which was the strangest thing for me.” Raising the undercarriage to reduce drag and improve lift should have been the first priority but it was possible that the crew left the wheels down to absorb the impact if they hit the ground, he added. The aircraft was fully loaded with fuel for the nine-hour flight to LondonNormal procedure would have meant leaving the flaps deployed until the aircraft reached a higher altitude, he said on his Pilot Blog channel. Premature retraction of the wing slats after take-off from Heathrow brought down a British European Airways Trident jet at Staines, Surrey, in June 1972, killing all 118 on board. In 1987, a Delta Air Lines jet crashed after taking off from Detroit without setting its flaps and slats. There was one survivor from 154 on board.• Boeing shares lower over safety fearsPilots speculated on aviation sites over a possible lack of thrust for the Boeing, which would have been fully fuelled and weighing some 230 tonnes for its nine-hour flight to London. The extremely rare phenomenon of a double engine loss could only be explained by something like a bird strike or fuel contamination, experts said.