United Airlines has been given permission to fly the Dreamliner again by the Federal Aviation Administration.
The FAA has issued a formal "air worthiness" for US airlines, but other country’s regulators are now expected to follow suit.
The US directive allows airlines to resume flights provided their battery systems are replaced.
It comes a week after the FAA allowed Boeing to replace battery systems with a new design.
All 50 787s in service were grounded in January over safety concerns.
United Airlines is currently the only US airline with 787s in its fleet.
A United statement said: "This is a good step forward. We are mapping out a return-to-service plan, and we look forward to getting our 787s back in the air."
The airline plans to begin domestic flights using the 787 in May but added: "We are currently planning to launch the Denver to Narita Tokyo route on June 10, although that will depend on successful completion of planned modifications ahead of that date.
"We are in the process of formulating our domestic flying plans and will be making additional schedule changes as we gain visibility into the timeline for completing the modification work."
Thomson was due to become the first UK airline to fly the 787 next month. It has not yet had confirmation of a delivery date from Boeing.
