As new Boeing 787s continue to stack up at Everett and others remain idle around the world, the airframer’s battery crisis is finally coming to a head as the FAA decides on whether to approve a company plan to return the aircraft to the skies.

If the FAA says yes, airline sources tell Aviation Week that the first 787s could begin operating again with an interim battery system modification as early as the third week of March. If it says no to the near-term proposal, then Boeing faces the far more painful and expensive alternative of developing and certifying a longer-term fix while the fleet remains grounded.

There are no easy decisions facing FAA Administrator Michael Huerta, who is scheduled to hear Boeing’s proposal from a delegation led by Commercial Airplanes President Ray Conner on Feb. 22. This marks the 38th day since the agency grounded the 787, one more day than the McDonnell Douglas DC-10 grounding in 1979.

The FAA response, which is not expected until Feb. 25 at the earliest, and perhaps not for several days beyond that, also requires approval from Ray LaHood, the U.S. transportation secretary. LaHood earlier raised the bar on conditions for a 787 reprieve by saying the aircraft will not return to service until authorities are “1,000% sure” it is safe.

Adding to the pressure on the FAA is the ongoing review of its original certification of the 787, as well as the yet-to-be-completed National Transportation Safety Board investigation into the first lithium-ion battery failure on a Japan Airlines aircraft Jan. 7 at Boston Logan International Airport. The NTSB, and its Japanese counterpart, the Japan Transport Safety Board (JTSB), are still evaluating the root cause of multiple battery failures that prompted a world-wide grounding of the 787 on Jan. 16.

As part of the investigation, engineers are looking at what could have caused a mechanical flaw inside the battery in service. While even the NTSB has stated that it has found no signs of overcharging, one part of the research still focuses on how a faulty charging process could lead to damage and subsequent overheating and smoke, ultimately causing the destructive sequence known as a thermal runaway. If confirmed, that would be a significant finding because it would redirect attention to the charging system, rather than the battery.

However both investigations so far have failed to pinpoint an exact cause, and with Boeing and its customers facing growing costs over the grounding, there are signs the FAA may be increasingly open to a compromise to get the jet back into service. The multi-point Boeing plan is thought to cover a phased approach toward a fully modified lithium-ion battery system. The short-term fix focuses on a new containment system for the existing unit, together with added venting ducts for smoke and additional monitors. It also is thought to incorporate additional crew procedures to check battery health and status via the engine indication and crew alerting system before, during and after flight.

Boeing is not discussing details of its proposal, but the supplementary venting understood to form part of the plan is expected to be routed to a dedicated overboard vent valve already built into the aircraft’s equipment cooling and ventilation system.