Investigators have disclosed that a diverted Air Canada Boeing 787-9's crew had to declare a Mayday four times over a low-fuel situation before being given approach clearance to Hyderabad.
The aircraft had originally been bound for Mumbai but was shuttled between alternate airports owing to capacity problems.
Transportation Safety Board of Canada states in a bulletin that it is "in contact" with India's accident investigation authority over the 19 September incident.
The aircraft (C-FGEI), which departed Toronto on 18 September, had been operating AC46 to Mumbai with 177 passengers and 14 crew members.
But Mumbai air traffic controllers cancelled the approach after a runway excursion involving another aircraft. The bulletin does not specifically identify this incident, but a SpiceJet Boeing 737-800 suffered an excursion shortly before the 787's arrival.
The Canadian bulletin says the 787 entered a hold for 1h but its crew then opted to divert to their alternate.
It does not identify the alternate but states that air traffic control informed the crew that they could not be accommodated owing to reaching maximum capacity.
The crew then chose to divert a second time to Hyderabad, after consulting with the carrier's operations centre, only to be informed by air traffic control en route that Hyderabad had already reached maximum capacity and could not handle the flight.
According to the bulletin Air Canada informed investigators that air traffic control "continued trying to divert the flight or attempted to place it in another hold", adding that the crew had to declare a Mayday over the aircraft's low-fuel situation four times before being cleared for a straight-in approach to Hyderabad's runway 09L.
Flight AC46, which has a scheduled duration of around 14h 30min, had been operating for around 17h at the time of arrival. The aircraft landed safely.