Brazilian airline Gol Linhas Aereas Inteligentes SA said it will replace 13 Boeing 737 Next Generation (NG) aircraft with the newer Boeing 737 MAX-8 between 2019 and 2021 as part of a plan to accelerate its fleet renewal and reduce debt costs.

In a securities filing on Wednesday, Gol said the decision to execute sale and leaseback agreements with investment firms Castlelake and Apollo Aviation comes during a favorable time for selling NGs.

Under the plan, 13 NGs will be returned upon receipt of the more fuel-efficient 737 MAX-8 jets, which will make up the backbone of the Brazilian carrier's fleet. Gol's planned capacity will not change as a result of the renewal plan, it said.

"These monetizations of our 737-800 NGs permit Gol to accelerate reduction of balance sheet leverage and increase liquidity," Richard Lark, Gol's chief financial officer, said in the filing.

The move will reduce the company's net debt by approximately 1.1 billion reais (US$280.48 million), it said.