Boeing flags flutter as an Airbus A380, the world's largest jetliner, takes part in a flying display during the 49th Paris Air Show at the Le Bourget airport near Paris
Boeing flags flutter as an Airbus A380, the world's largest jetliner, takes part in a flying display during the 49th Paris Air Show at the Le Bourget airport near Paris June 25, 2011. Reuters

An avalanche of airplane orders from the largest U.S. airlines may be on the way, with at least four major carriers in talks to buy fuel-efficient narrow-body planes to renew aging fleets.

AMR Corp (AMR.N), parent of American Airlines, is further along in discussions and is eyeing a large order for more than 250 narrow-bodies valued at more than $15 billion to be split between Boeing Co (BA.N) and its European rival EADS (EAD.PA) unit Airbus, sources close to some of the talks said.

Even a small order by American Airlines for Airbus planes would mark a significant shift in loyalty by the airline, which currently flies an all-Boeing mainline fleet.

Delta Air Lines (DAL.N) also is in talks with plane makers and says it aims to decide on an order for as many as 200 planes by the end of the year.

Southwest Airlines (LUV.N) and United Continental Holdings (UAL.N) reportedly are also talking about potential orders. US Airways Group (LCC.N), the only other major U.S. hub-and-spoke carrier, says it is not in talks to buy new planes.

Clearly the four big US airlines, which basically are American, the new Delta, the new United and Southwest -- all are talking about refleeting, said Adam Pilarski, senior vice president at AVITAS, an airline consulting company that also works with aircraft lessors and lenders. It's not a surprise, eventually they have to do it.

The U.S. airline industry is recovering from a years-long downturn thanks to capacity cuts and mergers.

American Airlines has announced orders for 130 737-800s and has been taking delivery for the last few years to replace aging, fuel-guzzling MD-80 aircraft. American Airlines currently has 128 737s and 247 MD-80s.

AMR Chief Executive Gerard Arpey said as long ago as 2008 that the company would consider the next-generation narrow-body offerings of both Airbus and Boeing, which are planning upgrades to their hot-selling narrow-bodies.

Airbus is putting a more fuel-efficient engine on its A320 and renaming it the A320neo.

Boeing is considering re-engining or fully redesigning its 737 but has delayed the decision even as Airbus amasses orders for its neo. A re-engined 737 would come to market faster but likely offer less fuel-efficiency than a redesigned version of the plane.

At last week's Paris Air Show, Airbus racked up firm orders for almost $50 billion of neos.

JetBlue Airways (JBLU.O) and Republic Airways Holdings (RJET.O) placed provisional orders for 120 of the planes.

The last stand for single-aisle airplanes is North America, said airline consultant Michael Boyd. He said Boeing was blown off the map in Paris as the neo piled up orders.

As U.S. airlines gear up for a potential order frenzy in the United States, Boeing insists airlines want a redesigned plane and are willing to wait for the company to fully assess its ability to produce it.

Speaking at the Paris Air Show, Jim Albaugh, chief executive of Boeing's commercial airplanes division, said he would not be surprised if Boeing 737 customers took a look at the neo, adding that he hoped Boeing could make a decision by year end.

THE WAITING GAME

But some experts say U.S. airlines may not be as patient as Boeing thinks. Talk of a Boeing split order underscores that reality, said Bob Mann, an airline consultant with RW Mann & Co and a former fleet planner for American Airlines.

(Boeing) have been hemming and hawing about this airplane for two years, and in the meantime Airbus has stolen a march on people who are willing to commit, Mann said.

He said he thinks American is threatening to split the order to force Boeing to commit now to a new plane, which Boeing says would instantly render the A320neo obsolete.

Airbus declined to comment on its talks with customers, but said it is making inroads into U.S. markets.

Speculation is rampant, too, that other new entrants to the narrow-body market could land orders that might have gone to Boeing or Airbus.

Last week, Guy Hachey, chief operating officer of Bombardier's (BBDb.TO) aerospace unit, said the Canadian company is targeting Southwest Airlines for a sale of its new CSeries airplane. Speaking at the Paris Air Show, he said Bombardier was in talks with other U.S. carriers as well.

Southwest spokeswoman Ashley Dillon said the carrier could not comment on any speculation regarding Bombardier, but added that her company did send representatives to the Paris Air Show.

AMR declined to comment on its talks with plane-makers. The airline has an average fleet age of 14.1 years, according to Airfleets.net. These numbers are at the high end of the range for the top five U.S. airlines.

But Pilarski at AVITAS said it was unrealistic to expect Boeing to win all the narrow-body orders -- even from long-time customers -- that soon will be up for grabs. The same is true for Airbus, he said.

Boeing and Airbus would not be able to produce that many planes in a very short period of time, Pilarski said.

They definitely will have to lose some because they cannot carry everything, he said.