Hedge fund firm Schultze Asset Management has increased its stake in Mair Holdings and asked the Minneapolis-based company to hold off on future acquisitions.

Mair formerly owned regional airline Mesaba Aviation, which emerged from bankruptcy recently and was purchased by Northwest. Mair still owns another regional carrier, Big Sky Transportation, and has said it wants to explore possible acquisitions both inside and outside the airline industry.

In a filing made with the Securities and Exchange Commission on Wednesday, Schultze disclosed it now has a 5.9% stake in Mair. It has been buying up shares since the beginning of the year.

The firm believes Mair is substantially undervalued based on the amount of cash it currently holds. It wants the company to distribute proceeds from the sale of Mesaba to shareholders as soon as possible and to hire an investment bank to explore a possible sale of Big Sky.

Former MD Sass analyst George Schultze runs Purchase, N.Y.-based Schultze Asset Management. The firm specializes in investments in distressed securities using an event-driven, value approach.