Grounded carrier Kingfisher Airlines has filed a revival plan with the Directorate General of Civil Aviation (DGCA), a senior government official said Tuesday, in an effort to renew its operating license before it expires at the end of the year.

Kingfisher, which has not flown since October, has estimated debts of $2.5 billion and owes money to banks, airports, tax authorities, plane leasing companies, and its staff.

The DGCA which suspended Kingfisher's licence to fly after months of cancelled flights and staff walkouts, has demanded a turnaround plan before the airline is permitted to fly again.

The DGCA wants all creditors to agree to the revival plan submitted by Kingfisher, and has not decided on its course of action, said the government official who has direct knowledge of the matter, speaking on condition of anonymity.

Bankers maintain they have the option of restructuring Kingfisher's loans for a second time, or infusing more capital, but they are awaiting a concrete revival or turnaround plan from the company, including capital injection by company chairman Vijay Mallya.

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The airline did not say where it would find the money it needs, but mentioned it was in talks with several parties, including one in London, for new cash, the source said.

Mallya's United Breweries Group plans to invest Rs. 6.52 billion in the airline as part of the turnaround plan it filed Monday, according to reports that were published in a local newspaper Tuesday.

Kingfisher has tried unsuccessfully to raise cash for more than a year. It said earlier this month it was in talks with Abu Dhabi's Etihad Airways and other potential investors about selling a stake in the carrier.