SAO PAULO, Dec 6 (Reuters) - Brazilian airline Gol had its credit ratings downgraded by both S&P and Fitch after hiring a financial advisor to help it conduct a "broad review" to its capital structure as it struggles with high debt.

Fitch on Wednesday joined fellow credit rating agency S&P in cutting Gol's rating to 'CCC-' from 'CCC+' on risks related to the carrier's debt restructuring, further pushing it into speculative territory.

Gol last week announced it had hired Seabury Capital to assist it in a capital structure review that included addressing liability management, financial transactions and "other measures" to enhance its liquidity.

The carrier would also look into reprofiling its financial obligations as well as its fleet for the near and medium-term, according to a securities filing.

"The recurring free cash flow pressure from high leasing and interest expenses despite improving operating performance are resulting in an unsustainable debt profile," Fitch said in a note to clients.

Gol reported a net loss in the third quarter and reduced estimates for annual earnings amid delayed deliveries of Boeing aircraft.

"The hiring of a financial advisor may prompt a broader discussion of the company's capital structure, given weak prospects for cash flow generation and the dependence on refinancing in the next two years," S&P said on Tuesday, adding its outlook for the firm's rating was negative.

That outlook reflected a potential debt restructuring that the agency would view as distressed and tantamount to default, it said, although adding it expects the carrier to maintain "good operating performance amid healthy demand and a very rational supply in the Brazilian airline market."

Gol's shares fell more than 9% on Monday before paring some losses the next day.

Among sell-side analysts, Citi had downgraded Gol earlier this month to "sell/high risk" noting that although the carrier's operating side was in a good place, that was not the case of its capital structure.

Goldman Sachs analysts said they would take no view on the potential outcome of the potential debt renegotiations, but added the move could be the first step towards a broad rearrangement of obligations with lessors and other suppliers.

That "could potentially alleviate pressure over balance sheet and short-term obligations," they added, noting that peer Azul had also announced a broad restructuring of its balance sheet recently. (Reporting by Gabriel Araujo and Alberto Alerigi Jr.; Additional reporting by Paula Arend Laier; Editing by Steven Grattan)