SAO PAULO, Jan 29 (Reuters) - A U.S. bankruptcy judge on Monday allowed Brazilian airline Gol to borrow the first $350 million of its proposed bankruptcy financing, which a company attorney said was "desperately" needed to maintain normal operations.

U.S. bankruptcy judge Martin Glenn approved the initial funding at a court hearing in Manhattan, despite voicing some concerns about the high cost of the overall $950 million loan. Glenn will consider approving the rest of the loan at a future hearing, and said he needs more insight into the financing costs.

"I'm not writing a blank check," Glenn said.

The loan has an interest rate that currently exceeds 15%, over $235 million in additional fees, and additional attorneys' fees that could be added to that cost later, according to court documents.

Gol attorney Andrew Leblanc said the initial funding was "desperately needed" to maintain Gol's operations and preserve relationships with the lessors who own Gol's fleet of 141 Boeing aircraft and who could stop maintenance work or seek to reclaim airplanes if they are not paid.

Gol's Sao Paulo-traded shares tumbled 33.6% on Monday to 3.93 reais, their lowest closing price since Dec. 22, 2016.

The company's shares have fallen by almost 50% since local media first reported earlier this month that the company was considering filing for bankruptcy. It now has a market value of 1.65 billion reais ($333.21 million).

In addition to the financing, Gol intends to use the legal protections of Chapter 11 bankruptcy to insulate its leases from outside interference, Leblanc said. A rival airline has already reached out to Gol's lessors in an attempt to "poach" Gol's aircraft, according to Leblanc.

Gol filed for Chapter 11 bankruptcy protection on Thursday with about $8 billion in total balance-sheet debt.

The company has $2.7 billion in liabilities coming due in the next 12 months, including $647 million for future air travel purchased by Gol's customers, $359 million owed to aircraft lessors, and $292 million owed to its lenders.

The company, which ranks second in market share among airlines flying domestically in Brazil, is the latest Latin American air carrier to file for bankruptcy in the United States.

Other airlines that have recently completed bankruptcy restructurings in the U.S. include LATAM Airlines, Grupo Aeromexico SAB, and Avianca Group International Limited.

Despite strong post-pandemic demand, Gol has struggled with the pandemic's lingering impact and supply-chain issues involving Boeing, including the 2019 grounding of its 737 MAX jet and delayed delivery of new aircraft that Gol intended to add to its fleet in 2023.

Gol is 53% owned by Grupo Abra, which also owns Colombia-based Avianca. ($1 = 4.9518 reais) (Reporting by Dietrich Knauth in New York and Gabriel Araujo and Andre Romani in Sao Paulo Editing by David Alire Garcia, Alexia Garamfalvi and Matthew Lewis)