A plane with 153 people on board had five minutes' worth left on a recent flight in India, according to local media.
The A320Neo aircraft was airborne for four hours on Monday as it circled over Delhi before being diverted to Lucknow around 420km away.
However after visibility suddenly dropped above Lucknow, the pilots attempted to head to Prayagraj, Allahabad some 200km away, only to turn towards Lucknow again after seven minutes.
“When it touched down, the A320Neo had only 200kg or 5 minutes of flying time left," a source told the Times of India.
A senior pilot told the publication: "It's a miracle they landed."
He added that the decision to divert to Prayagraj over choosing to carry out a fully automated landing at Lucknow was "sacriligious".
The standard flight time from Mumbai to Delhi is around two hours.
A Vistara spokesman told the Standard: “Flight UK944 operating Mumbai-Delhi on July 15, 2019, initiated a diversion to Lucknow due to bad weather over Delhi. However, over Lucknow, the visibility suddenly dropped and a safe landing was not possible.
“The crew then considered alternative airfields, including Kanpur and Prayagraj, to land in comparatively better weather conditions.”
He added: ”The unexpected drop in visibility at the destination alternate was the main reason why the aircraft ended up in a low-fuel situation despite carrying excess fuel over and above the required Flight Plan Fuel as per regulations.
“Safety of passengers and crew was kept at the highest priority throughout the flight.”
The flight finally touched down safely in Delhi at around 1.35am after refuelling at Amausi airport, having departed Mumbai at 2.40pm.