Boeing has warned airlines of possible engine icing problems on some of its new planes.
The US plane maker says aircraft with a specific General Electric engine should avoid flying near thunderstorms that might contain ice crystals.
Boeing spokesman Marc Birtel said the company issued the advisory after ice crystal formation sometimes diminished engine performance.
"To reduce chances of ice crystal conditions, Boeing recommends that operators fly at least 50 nautical miles from thunderstorms that may contain ice crystals," Boeing said.
The advisory covers Boeing planes with General Electric's GEnx engine. Boeing said GE was "working diligently" to deal with the issue and that corrective changes "will be introduced into the fleet as soon as they are available".
It is the latest problem to confront the 787. Earlier this year, it was grounded after two planes suffered from smouldering batteries. Flights resumed after Boeing redesigned the battery system.
:: Boeing is soliciting bids from more than a dozen locations that want to build the new 777X plane.
Company spokesman Doug Alder said requests for bids began going out on Friday and Boeing wants the proposals returned in a few weeks. It hopes to make a final decision early next year.
Mr Alder would not name the locations but said each had asked for the chance to compete for the 777X work and met the company's qualifications. Production of the plane will mean thousands of long-term jobs for whichever location Boeing selects.
Boeing had initially offered to build the 777X in Washington state, but the machinists union rejected a proposed contract. The state still plans to compete for the work.