The 787 has been grounded since mid-January because of smouldering batteries. Federal authorities have approved Boeing's redesigned battery system.
Boeing CEO Jim McNerney says the new battery setup has been installed on 10 787s that belong to airlines, and on nine more that have been built but not delivered.
He says "the bulk" of airline-owned 787s will get the battery fix by mid-May. Each installation takes about five days.
Boeing has kept producing the 787 even though it was grounded. But it can only collect the cash from airlines when it delivers the planes — so restarting deliveries is important to the company.