Struggling Skymark Airlines Inc. is expected to return to the black in the fiscal year ending on Thursday by posting an operating profit of more than ¥1.5 billion ($13 million), sources familiar with the matter said Friday.

The company's business has been improving following restructuring efforts, including slashing unprofitable routes, and due to declining fuel costs because of oil price plunges, the sources said.

Skymark, set up in 1996, filed for bankruptcy with the Tokyo District Court in January last year, after plans to shift to bigger aircraft failed and left Japan's third-biggest airline in financial distress.

It is now expected to complete its rehabilitation proceedings around next Monday, the sources said.

The airliner posted an operating profit of ¥15.2 billion in the fiscal year ended in March 2012 but fell into an operating loss of ¥2.5 billion in the year to March 2014.

The operating loss expanded to ¥11.2 billion in the April to December 2014 period before filing for bankruptcy.

It is now paying creditors after receiving ¥18 billion in capital from rehabilitation sponsors, including private equity firm Integral and ANA Holdings Inc.