The ability of the Boeing 787 to operate on extended operations (ETOPS) routes immediately after the grounding order is lifted will remain an uncertain issue while the certification process is ongoing.
The US Federal Aviation Administration (FAA) declines to comment for now on the status of the 787's ETOPS certification.
"It is premature to discuss the status of 787 ETOPS approvals before the certification programme is finished," the FAA says.
Boeing, however, is confident that the unresolved battery malfunctions that have grounded the 787 fleet for two months will not change the aircraft's ETOPS qualification.
"There is no expected change to ETOPS certification," Boeing says.
The ETOPS issue is critical to the 787's successful return to flight.
The 787 was certificated by the US Federal Aviation Administration (FAA) in September 2011 for 180min ETOPS flights, meaning it could operate on one engine up to 3h flying distance from an eligible runway.
ETOPS certification is necessary for airliners to fly most trans-Pacific routes and even some flights overland, such as over remote parts of Australia.
To obtain ETOPS certification, an aircraft manufacturer has to prove the electrical and mechanical systems are reliable enough to function until a twinjet aircraft can reach a runway on only one engine.
Boeing originally hoped to receive 330min ETOPS certification for the 787 at entry into service in October 2011. Instead, it entered service with 180min ETOPS certification. The 787 lacked at that time a required low-fuel alert system that the FAA added to the ETOPS standard after the aircraft systems were designed.
At the time of the battery grounding in January, Boeing and the FAA were negotiating how the 787 could achieve the original 330min certification goal.
The 787 now has a low-fuel alert system for the flight crew and meets all of FAA's requirements for 330min certification, Boeing says.
But the FAA had not decided how to handle ETOPS how to deal with unresolved technical glitches from in-service experience.