Airlines in India are asking the government to help them obtain unsecured credit from oil companies and airports, as fuel-price increases push them deeper into losses and imperil their survival.

Competition and aggressive pricing are stopping fares from rising to reflect higher input costs, the Federation of Indian Airlines said in a letter sent to the aviation ministry's top bureaucrat last week and obtained by Bloomberg News. Ujjwal Dey, a spokesman for the group, confirmed the letter and its contents, but couldn't immediately comment further.

Airlines are "facing challenging times and substantial losses in the domestic environment," the communication addressed to Aviation Secretary Rajiv Nayan Choubey said.

The plea is the latest signal of the crisis facing airlines in India, where the world's fastest-growth in air travel has created a capacity glut that's keeping fares below cost, while fuel prices and a weaker rupee squeeze them further. Jet Airways India Ltd., the market's second biggest player, is struggling to stay afloat after delayed payments to staff and lessors, and is in talks with investors to raise funds.

The FIA consists of Jet, InterGlobe Aviation Ltd.'s market leading IndiGo, SpiceJet Ltd. and Go Airlines India Ltd., which together account for almost 80 percent of the domestic market.

Losses at Indian carriers will balloon to as much as $1.9 billion in the year ending March 2019, and they need to raise more than $3 billion in working capital in the near term, according to Sydney-based consultancy CAPA Centre for Aviation. Most of them have cash balances that can cover expenses for only two to three weeks, according to CAPA.

"There is a considerable cash-flow mismatch between costs and revenues earned," the letter said, urging the aviation ministry to assist airlines in obtaining a penalty-free, one-month unsecured credit line from oil companies, as well as state-run Airports Authority of India and private airports. Carriers already receive credit from both groups on an ad hoc basis.

Base air fares can be as low as 1 rupee (1 cent) in India, while states charge taxes as high as 30 percent on jet fuel. Airlines are unable to pass on those costs to customers without hurting passenger growth, the FIA said. The rupee has weakened almost 11 percent this year against the dollar, driving up financing costs on overseas borrowings.

Indian carriers would need to raise fares by 12 percent to offset the double blow from fuel and currency depreciation, and their eagerness to fill seats and gain market share will prevent ticket prices from going up, according to CRISIL Ltd., the local unit of Standard & Poor's. They are facing their worst losses in a decade, it said earlier this month.