Teams of Boeing engineers and technicians began fanning out across the globe Monday to modify the battery systems of 50 of the company’s 787 Dreamliner jets and get the grounded fleet back in the air.

The U.S. Federal Aviation Administration on Friday approved Boeing’s plans to install modification kits intended to reduce the risk of overheating in the planes’ lithium-ion batteries. The planes have been grounded for three months.

A team of around 30 technicians arrived in Japan over the weekend and began work on the modifications early Monday, Larry Loftis, vice president and general manager of the 787 program, said in a telephone briefing with reporters. All Nippon Airways and Japan Air Lines are the biggest operators of the Dreamliner.