Safety regulators are poised to approve within days a plan to allow Boeing to begin flight tests of the 787 Dreamliner with a fix for a its volatile batteries, a critical step towards returning the grounded aircraft to service, two sources familiar with the matter said on Wednesday.

The Federal Aviation Administration is expected to sign off on a "certification plan" allowing Boeing to carry out the flight tests to demonstrate whether authorities can lift a flight ban that sent shockwaves around the airline industry seven weeks ago.

"You could see the ���cert plan' approved in the next few days," one of the sources said. Both spoke on the condition of anonymity because the discussions are confidential.

The FAA said it would announce the plan when approved. Boeing declined to comment.

(Reporting by Tim Hepher in Berlin and Alwyn Scott in New York.)