OSO — Swooping over a landscape of unspeakable sadness and death, President Barack Obama took an aerial tour Tuesday of the place where more than three dozen people perished in a mudslide last month. He pledged a nation’s solidarity with those who are enduring “unimaginable pain and difficulty” in the aftermath of the destruction.“We’re going to be strong right alongside you,” Obama promised the people whose lives were upended when a wall of mud and water swept away the hillside on March 22 and took with it at least 41 lives and dozens of homes. Obama first boarded a helicopter to survey the awful scene.Evidence of the mudslide’s power was everywhere: trees ripped from the ground, a highway paved with mud and debris, a river’s course altered. And in the midst of the awful tableau, an American flag flying at half-staff.Even as the president flew overhead, the search for bodies continued below. Two people were still listed as missing.Back on the ground, the president gathered at a community chapel in the small town of Oso, about an hour northeast of Seattle, to mourn with families of the victims. He met separately with emergency responders before speaking in a small brick firehouse about all he had seen and heard on a clear, sunny afternoon.“The families that I met with showed incredible strength and grace through unimaginable pain and difficulty,” Obama said. Then he offered them a promise.