Boeing is looking at several design changes to its lithium-ion batteries that could lower Dreamliner's battery risks and help get the grounded jets back in the air.

According to a Wall Street Journal report that cited unnamed government and industry officials, the jet maker is looking for modifications within the battery that could reduce the chances of heat or fire spreading.

The report added that Boeing hopes to ship the new batteries as early as the end of this month and get the flights back in the air by March.

Meanwhile, the US regulators suggested that it would take weeks to conclude the official investigations.

The US authorities have indicated that the battery in itself may not be the cause of trouble as they extend investigations to related systems. The National Transportation Safety Board (NTSB) said that it may be weeks before the actual problems behind the issues that forced 787 groundings are discovered.

"I would not want to categorically say that these batteries are not safe," said Deborah Hersman, head of the NTSB.

"Any new technology, any new design, there are going to be some inherent risks. The important thing is to mitigate them."

However, the authorities have allowed Boeing to make a test-flight from Texas to the company's facility in Washington, under stiff conditions. Boeing has clarified that a craft that was scheduled for delivery to the China Southern Airlines will make a ferry flight.

But despite Boeing's hopes to resume Dreamliner services by March, some experts consider the timeline is unrealistic. Talking to Reuters, an unnamed official in Tokyo said that, "The investigation will continue as scheduled. Resuming flights in March ... seems far too optimistic to me".

Shukor Yusof, an aviation analyst with Standard & Poor's told BBC that, "until the regulators can find out what exactly went wrong with the batteries, and figure out a solution to the problem it is unlikely that they will allow the planes to fly".

NTSB's comments of the extended time period for the probe have also fuelled concerns that the issue may prove more costly for Boeing than estimated before. The jet-maker has already suspended 787 deliveries till the investigation concludes.

Dreamliner groundings have caused hundreds of flight cancellations and affected thousands of travellers. The All Nippon Airways (ANA), Boeing's first and by far the biggest 787 customer, has said that it will cancel 1,887 flights from March 1 to 30 affecting more than 25,000 passengers. According to Reuters, ANA has not received any information on Boeing's latest battery plans.