All Boeing 797 Dreamliner airplanes were grounded last month because of a number of technical problems and even caused All Nippon Airways to make an emergency landing.
The cause of the problems presumably lies with the batteries of the planes. The FAA is still investigating the incidents.
However, Boeing has sought permission of the FAA to operate test flights with the Dreamliner planes. This could be an indication that Boeing found a solution to the technical issues. It is not clear yet if the FAA will grant their request. It obviously will take a while before airlines will be able to use the Dreamliner airplanes for passenger flights.