NEWARK — More fliers out of Newark Liberty International Airport will enjoy the comforts of home while in the air, with an announcement that the airport's biggest carrier will add flat-bed seating and broadband wi-fi capability, and nearly double the overhead storage space on many of its jets.

United Continental Holdings, the parent company of United and Continental Airlines, said today it was spending $550 million on improvements to many of its jets by next year.

A United Continental spokeswoman, Mary Clark, declined to say whether the cost of the upgrades would be passed on to passengers.

Continental and United Airlines, which will begin flying as a single carrier under the United name next year, account for more than two-thirds of all flights in and out of Newark Liberty. The parent company announced that Continental will begin offering economy-plus seating, a service featuring extra leg room already available on United flights.

Starting next month, the company will begin installing flat-bed seats, on-demand video programming and iPod service on 12 Boeing 767-400s flown by Continental and 14 of United’s 767-300s, which fly trans-Atlantic, South and Central American and Hawaiian routes.

Flat-bed seats work like one-person futons, reclining until the seat back is parallel to the floor and essentially becomes a bed. Flat-bed seats typically have more leg room while in the upright position, and are slightly wider than normal seats.

Flat-beds have become increasingly common among foreign carriers and U.S. airlines with long-distance overseas routes, including United and Continental, which already offer them on some flights.

The investments are among a broad range of upgrades, including the purchase of new aircraft, by United Continental since the carriers merged in October. United Continental CEO Jeff Smisek announced the new amenities today at the Global Business Travel Association’s annual convention in Denver.

Robert Mann, an airline analyst in Port Washington, N.Y., said the investments were part of Smisek’s effort to "make good on his vow to make this a truly world class airline."

"It’s basically a mix of importing some of the best service available from United, adding some new technology, trying to be superior to Delta in the domestic market and then trying to compete with some of the foreign flag carriers," Mann said.

Beginning in March, United will double the amount of overhead luggage space on all 152 of its Airbus A319 and A320 jets, and refurbish their interiors, United Continental said.

The company said it is now in the process of choosing a provider of streaming video entertainment on its 747-400 aircraft, which will let passengers screen movies and other entertainment on hand-held devices.

Bob Herbst, an analyst at airlinefinancials.com, said the upgrades are long overdue.

"International airlines like Singapore, Cathay, Emirates, etc. have a far superior airline product than what U.S. carriers have," Herbst said in an e-mail.

"It’s long past time U.S. airlines clean up their act and put out a better product for the passengers. For too many years the only priority for U.S. airlines has been to make the airline travel as cheap as they could get it."