Japan's biggest airline, ANA Holdings Inc (9202.T), will buy a stake of less than 20 percent in Skymark Airlines Inc (SKALF.PK) as part of a rescue plan for the bankrupt domestic budget carrier, people familiar with the matter told Reuters.

Private equity firm Integral Corp has secured a majority stake, according to the sources. ANA will acquire less than 20 percent. If it held 20 percent or more, it could be forced to surrender some of its landing rights at Tokyo's Haneda airport.

ANA's investment comes after Skymark filed for bankruptcy in January. Skymark agreed a 9 billion yen ($76 million) deal with Integral earlier this year and has been seeking other parties to help it turn the business around.

Integral and ANA have made agreements on matters including the eventual relisting of Skymark and sustaining the number of employees, the sources said.

ANA and financial institutions initially wanted to take a majority stake in Skymark, an idea that Integral opposed, leading to the current agreement, the sources said.

ANA plans to help Skymark through joint-flights, fuel shipments, and equipment safety, they added.

Integral and Skymark could not be immediately reached for comment. ANA spokesman Ryosei Nomura said the company had nothing it could announce at this moment.

ANA has invested in other low cost carriers in the past, including Air Do and Solaseed Air.