WASHINGTON (Reuters) - U.S. Federal Aviation Administration (FAA) chief Steve Dickson is “100% confident” in the safety of the Boeing 737 MAX but says the airplane maker has more to do as it works to improve its safety culture. Dickson on Wednesday signed an order to allow the best-selling plane to resume flights after it was grounded worldwide in March 2019 following two crashes that killed 346 people and led to Boeing’s biggest crisis in decades. The order will end the longest grounding in commercial aviation history and paves the way for Boeing to resume U.S. deliveries and commercial flights by the end of the year. “We’ve done everything humanly possible to make sure” these types of crashes do not happen again,” FAA Administrator Dickson told Reuters in a 30-minute telephone interview, adding the design changes “have eliminated what caused these particular accidents.” The FAA is requiring new training to deal with a key safety system called MCAS that is faulted for the two fatal crashes as well as significant new safeguards and other software changes. “I feel 100% confident,” said Dickson, a former airline and military pilot, who took over as FAA administration in August 2019 and took the controls for a 737 MAX test flight in September. In a video message released on Wednesday, he said that the 20-month review was “long and grueling, but we said from the start that we would take the time necessary to get this right.” Dickson said he emphasized to Boeing the importance of safety. “I understand they have a business to run but they don’t have anything if they don’t have a safe product,” Dickson said. Dickson suggested Boeing has more to do to improve safety. “They have taken some actions, but it’s going to take more then putting new processes in place and moving boxes around the organization chart. Cultural changes take a long time to take effect and we’ve got to be skeptical,” he said. Boeing said it is “committed to learning from our mistakes to build a safer future so accidents like this never happen again.” The FAA has also come under harsh criticism over its certification of the 737 MAX. The U.S. House of Representatives approved a reform measure on Tuesday of the FAA’s aircraft certification program. Representative Peter DeFazio, a Democrat who chairs the Transportation and Infrastructure Committee, said the FAA failed to properly ensure the safety of the 737 MAX, and called aircraft certification “a broken system that broke the public’s trust.” Dickson acknowledged there was fragmented communication within the FAA and between the FAA and Boeing during the 737 MAX certification. He noted the agency is adopting certification reforms and improvements in response to outside reviews of the 737 MAX certification. The FAA could take new enforcement actions or issue new civil penalties against Boeing over the 737 MAX and on other issues stemming from a 2014 settlement agreement, but Dickson did not elaborate. “It’s a matter of our review of what Boeing’s actions have been up to this point,” Dickson said. “There is going to be more that we’ll be able to talk about that in the coming weeks and months.” The MCAS, or Maneuvering Characteristics Augmentation System, is designed to help counter a tendency for the nose of the 737 MAX to rise up, known as a pitch up, and it could be activated after data received from one of two sensors. Boeing says inputs from both sensors on the MAX will be used after the updates but the European Union Aviation Safety Agency has called for a third synthetic sensor to provide independently computed data. Dickson said the FAA will consider requiring that synthetic sensor in future 737 MAX versions, but has made no decisions. Dickson said he said expects other international regulators will “complete their work within a relatively short period of time.”