DALLAS — Airlines including AMR Corp., UAL Corp. and Hawaiian Holdings agreed to sell the company whose communications systems link pilots with air-traffic controllers to buyout firm Carlyle Group. Terms of the sale of ARINC Inc. weren't disclosed.

AMR, parent of American Airlines, will post a $140 million gain on the transaction, the Fort Worth, Texas-based company said yesterday in a regulatory filing. The company said in October it might sell assets including its 30 percent ARINC stake to cut debt. Chicago-based UAL, parent of United Airlines, will record a $40 million gain, according to a separate U.S. Securities and Exchange Commission filing.

ARINC is "no longer a core business and it's nice to have the cash," George Hamlin, managing director of consultants Airline Capital Associates Inc. in Fairfax, Va., said yesterday in an interview. "Airlines need to concentrate on getting their own financial houses in order."

Annapolis, Md.-based ARINC has been owned by airlines since its formation in 1929, spokeswoman Linda Hartwig said in an interview. Its systems are behind 13 million air-travel messages a day, or 70 percent of global air-to-ground communications for airlines. After diversifying, three-quarters of its annual revenue of more than $900 million is from defense and aerospace customers, she said. The company has about 3,300 employees worldwide.

ARINC said in its annual report that its other owners include Air Canada, Air France-KLM Group, Alaska Air Group Inc.'s Alaska Airlines, Boeing Co., British Airways Plc, Delta Air Lines Inc., Hawaiian Holdings Inc. (parent of Hawaiian Airlines), Deutsche Lufthansa AG, Scandinavian Airlines System AB, Swiss Air Transport, Taca International Airlines and US Airways Group Inc.

Airlines already have shed ownership in businesses including catering and the Orbitz online travel company, Hamlin said.

Since the Sept. 11 terror attacks, ARINC has developed a system that would allow so-called first responders to an emergency such as police officers and firefighters to communicate with one another.

"We feel our company has huge potential," Hartwig said. "The airlines are not able to place a lot of equity in our company. In order to continue to grow, we needed a private-equity investment."

AMR and UAL said the sale should close by Oct. 31.