In a significant victory for Airbus, the European aircraft maker has broken into Japan, announcing on Monday a deal to sell 31 A350 aircraft valued at $9.5 billion based on list prices to Japan Airlines.
Japan is a strategic Boeing market where the U.S.-based plane maker has an around 80 percent market share.
At the same time, Boeing will "probably make inroads into European-based carriers, which have been historically Airbus-focused. They're looking into each other's markets to gain share," said Timothy Ross, an analyst at Credit Suisse.
Last month, Lufthansa, which traditionally leans toward Airbus, decided to split an order for 59 wide-body jets between Boeing and Airbus. Air France last year also split a 50-plane order between the two.
Both Airbus and Boeing have been jockeying for orders from Japan as JAL and Nippon Airways are preparing to update their fleets.
ANA is expected to purchase around 25 aircraft. JAL currently flies around 214 planes in total. All Nippon Airways, Japan's largest airline, flying around 230 aircraft, is also considering whether to order Airbus jets and it is expected to announce its decision soon.
Competition for these orders is only likely to become keener as carriers look beyond the initial price discounts they might receive for large orders from a single manufacturer.
When it comes to having more than one make of plane, "there are definitely some costs involved," including pilot and maintenance qualifications, said Andrew Orchard, an analyst at CIMB.
While carriers may get better discounts from ordering only one type of plane, "if you have another one, then you can go back and forth on negotiations," he said. "Otherwise, they can charge you whatever they want."
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"You might get a discount on the aircraft, but in the after-sales market, you might pay significantly more. Not getting a good deal on those upfront might be more costly than not getting a good deal on the aircraft itself," Ross said. "There's certainly competitive tension between the two airframers when you do operate both."
Airlines globally are looking to retire aging, less fuel-efficient planes as jet fuel prices, responsible for at least 50 percent of operating costs, rise; the savings can be significant, with Reuters reporting Lufthansa's new jet purchases should cut the carriers fuel consumption by 25 percent and lower unit costs by around 20 percent compared with older models.
"The higher the jet fuel price goes, the more impetus is added for older aircraft retirement," Ross said. JAL has a large number of aircraft due for retirement, he noted.
There's another reason carriers, such as JAL, are looking to diversify their planes.
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"They've learned their lessons from the 787," said Shashank Nigam, CEO at SimpliFlying, a Singapore-based aviation marketing strategy firm. Boeing's 787 Dreamliner model faced a rocky launch, with a number of production delays followed by in-service incidents; early this year, regulators globally grounded all 787s for four months. ANA and JAL are two of the biggest Dreamliner operators.
"It's critical for the brand. They can tap on both suppliers," Nigam noted. "It's almost like an insurance policy."
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1