The A350 would be the second large passenger jet to fly on Lithium-Ion batteries for backup electrical power after the Dreamliner, which pioneered their use in passenger transport to support an increasing array of electrical systems.
The top-of-the-line F-35 U.S. fighter jet also uses Lithium-Ion batteries, designed to kick in at short notice and start moving wing surfaces in an emergency so that pilots can land.
Airbus said last week it had a plan B for its battery design and time to respond to any changes in rules for their use.
However, experts say that if the 787 probe fails to provide clear answers soon, pressure may build for Airbus to pre-empt the findings and switch solutions to head off development risk.
The planemaker plans to make the maiden flight of its newest airliner, developed at an estimated cost of $15 billion, around the middle of the year. This will be followed by a year of flight trials and a complex certification process, during which the distraction of re-engineering could cause notable delays.
The A350 is due to be delivered in the second half of 2014, around two years behind its original schedule.
The company has said the targets are challenging.
Investigators in the United States and Japan are examining how the Lithium-Ion main batteries in the 787 suffered a thermal runaway, or overheating that can burn a battery out and create a fire that is difficult to extinguish.