Police boats combed the banks of the Potomac River on Friday, slowly scanning the shoreline under rainy skies as investigators sought clues into the midair collision that killed 67 people and raised questions about air traffic safety around the nation’s capital. No one survived the Wednesday night collision between the commercial airliner and an Army helicopter. The remains of 41 people had been pulled from the river as of Friday afternoon, including 28 that had been positively identified, Washington, D.C., Fire Chief John Donnelly Sr. said at a news conference. He said next of kin notifications had been made to 18 families, and that he expects the remains of all 67 people who died to eventually be recovered. The wreckage of the plane's fuselage will probably have to be pulled from the water to get all the bodies, he said. “This is heartbreaking work,” Donnelly said, noting that more than 300 responders were taking part in the effort at any one time, including teams of divers and two U.S. Coast Guard cutters, at least one of which carries a crane. “It’s been a tough response for a lot of our people.” It was unclear how long the recovery operation would take. “We’re working as fast as we can,” he said. "We need your patience.” Although Ronald Reagan National Airport has reopened, two of its three runways remain closed to keep aircraft from flying over the crash scene while taking off or landing, said Terry Liercke, the airport's vice president and manager. Roughly 100 flights were canceled Friday. MORE: https://www.wtsp.com/article/news/nation-world/midair-collision-kills-67-people-deadliest-us-air-disaster-in-decades/507-3e711c59-52a5-4337-b3f4-be317368d9e8