Shares in Airbus parent EADS cruised to their highest level in nearly four years on Wednesday, boosted by hopes of a big share of an airplane order set to be announced by American Airlines.

Sources told Reuters the board of parent AMR was voting overnight on an aircraft order worth more than $20 billion for several hundred aircraft, expected to be split between Boeing and Airbus.

The airline is expected to unveil the order for Boeing 737 and Airbus A320neo-family jets at around 1100 GMT on Wednesday.

American Airlines last ordered Airbus planes in the late 1980s and declared in 1996 Boeing would be its exclusive airplane provider through 2018. If Airbus wins all or even part of a big order from the carrier, it would be a coup.

We're talking about a massive order, and EADS will probably get a big chunk of it. EADS's stock has risen a lot lately, but they still have a pretty strong momentum, a Paris trader said.

In late morning trading, EADS shares were up 2.9 percent at 24.62 euros after rising as much as 4.3 percent in brisk volume.

The deal is also expected to provide a boost to General Electric and France's Safran which look poised to win a deal for the engines, industry sources said. Shares in GE partner Safran rose 3.6 percent to 28.71 euros in Paris.

Estimates for the overall size of the deal expected to be split between Airbus and Boeing range from 200 to 400 airplanes, with options for later sales. A source close to the talks said the higher number was within the realm of possibility.

French brokerage Cheuvreux said the deal could trigger a chain reaction of purchases by Delta , United Continental Holdings , Southwest and US Airways .

The board vote follows tense haggling that saw Boeing agree to match Airbus and update its best-selling 737 medium-haul jet with new engines to offer fuel savings, industry sources said. That marks a retreat from ambitious plans for a full redesign.

AMR, Boeing and Airbus declined to comment on the talks.

The market for narrowbody jet sales is estimated at $2 trillion over 20 years and is split between Boeing and Airbus, whose A320 has made substantial U.S. inroads.

The European company said last year it would put a more fuel-efficient engine in its A320 family and call it A320neo. The A320neo aircraft is scheduled to enter service in late 2015.

Boeing has debated whether to redesign its 737, a workhorse for airlines around the world, or put a new engine in it.

Experts say re-engining should deliver fuel savings of 15 percent. Up to 25 percent could be achieved by an all-new plane but it would cost five times more to build, or $10 billion.

Airbus dominated the Paris Air Show last month with orders for the A320neo, putting pressure on Boeing to respond, and the contest for American's business has brought the battle over strategy between the world's leading planemakers to a head.

(Additional reporting by Kyle Peterson and Karen Jacobs; Editing by Jon Loades-Carter)