Despite the route being longer, the flight took almost two hours less thanks to tailwinds — winds that blow in the same direction as an aircraft and thus make it go faster. Flying west means facing strong headwinds (that decreases an aircraft's actual ground speed), and flying east means getting strong tailwinds, which does the opposite," said a senior AI official. "While taking the (western) Atlantic route to SFO, we usually face headwinds of 24kmph. This means that if our aircraft is doing 800kmph, its actual ground speed is 776kmph. A shorter flying time on the Delhi-SFO route — from an hour in summer to three hours (in winter) — would mean huge fuel savings for the airline.

Source: Times of India October 22, 2016 22:41 UTC