Boeing officials said it's not uncommon for airplane fixes to be applied when the root cause isn't known. The fixes they plan for the 787 should prevent battery fires and runaway heat buildups regardless of the root cause, they said.
Boeing executives downplayed the parts of the incident that have most worried travelers. They said the only fire was on a connector on the outside of the battery box in the Japan Airlines plane, not in the battery itself. The white gas billowing out the side of the plane wasn't smoke, but electrolyte in gas form, they said.
"We have not ruled out a fire in the battery," NTSB spokesman Peter Knudson said after Boeing's comments. The NTSB is leading its own investigating of the Boston fire, and is participating in the investigation in Japan.
"We saw a lot of charring inside the battery. The evidence is consistent with very high temperatures," he said.
Boeing is also replacing the circuitry on the U.S.-made battery charger. The changes will cap the battery's maximum charge, and will also stop draining power sooner, to prevent a so-called deep-discharge. The changes are designed to reduce the amount of energy in the battery, which should reduce its potential to generate heat, Boeing officials said.