Mesa Air Group will sell 18 Embraer aircraft to United Airlines for about $229.1 million and use the proceeds to cut debt, the regional airline operator said on Tuesday.

Shares of Mesa, the parent company of Mesa Airlines, rose more than 10% before the bell.

Most of the aircraft of the Phoenix, Arizona-based company are operated under an agreement with United, where they fly under the United Express brand.

Mesa completed the sale of eight of the 18 aircraft on Dec. 31 and expects to close the rest by the end of this month.

The company expects to use $142.4 million of the gross proceeds from the sale to pay off associated debt, Mesa said in a regulatory filing.

Mesa also said it had entered into a separate deal with a third party on Dec. 24 to sell 15 used Bombardier CRJ-900 airframes for about $19 million.

The company intends to use the cash from that transaction to pay down its loan with the U.S. Treasury.