Kingisher Airlines' planned investment of 6.5 billion rupees is not enough to restart operations at the grounded Indian carrier, a senior government source said on Friday.

The revival plan, which Kingfisher Chairman Vijay Mallya filed last month with India's Directorate General of Civil Aviation (DGCA), does not include details on payment of dues to airports and may not guarantee a reliable service, said the source, declining to be named.

DGCA suspended the airline's licence to fly in October after months of cancelled flights and staff walkouts.

Kingfisher, once India's second-largest airline, is estimated to owe $2.5 billion in debt to banks, staff, vendors and others. The airline, which has not flown since October, has tried unsuccessfully for over a year to bring in new investors.