Boeing has found a way to fix battery problems on its grounded 787 Dreamliner jets that involves increasing the space between the lithium ion battery cells, a source familiar with the U.S. company’s plans told Reuters.

“The gaps between cells will be bigger. I think that’s why there was overheating,” said the source, who declined to be identified because the plans are private.

A spokeswoman for the U.S. National Transportation Safety Board declined comment on the Reuters report or any Boeing plan to return the 787s to the air.

“The decisions to return the airplane to flight will be made by the FAA and only after Boeing has demonstrated to them that the solution is adequate,” Kelly Nantel said. “We continue to investigate the cause of the short circuiting.”

A spokeswoman from the U.S. Federal Aviation Administration declined to comment. Boeing declined comment on details of any battery fix it may be considering.

The 50 Dreamliners in commercial service were grounded worldwide last month after a series of battery-related incidents including a fire on board a parked plane in the United States and an in-flight problem on another jet in Japan. Until the Dreamliner is cleared to fly again, Boeing will be starved of delivery payments.

The logical solution for Boeing would be to install ceramic plates between each cell and add a vent to the battery box, Kiyoshi Kanamura, a professor at Tokyo Metropolitan University who has conducted research with several Japanese battery makers, told Reuters on Tuesday.

Earlier on Wednesday, the chairman of state-run Air India AIN.UL said Boeing is hopeful of getting the Dreamliner back in service by early April.