Just after 8:43 p.m. on Jan. 29, an air traffic controller at Ronald Reagan National Airport in Washington, posed a question to the pilots of American Airlines Flight 5342: Could they land at a different runway?

There was nothing unusual about the request or the pilots’ assent to it. But the decision to switch runways was fateful, bringing the plane closer to the Army Black Hawk helicopter that it would collide with in a crash that killed 67 people.

Exactly what happened is still being pieced together. The National Transportation Safety Board is recovering and examining wreckage from the icy Potomac River. The safety agency is expected to publish a preliminary report in the coming weeks, but a more thorough accounting probably won’t arrive for a year or two.

But, based on the details that have emerged so far, the pilots in the American regional jet appear to have acted as expected, according to aviation safety experts and half a dozen airline pilots who have flown to and from Reagan airport. There appeared to be little that they could have done differently, these experts told The New York Times.

“There wasn’t anything to do. It was a normal day at Reagan,” said Shawn Pruchnicki, a former airline pilot and an assistant professor at the Center for Aviation Studies at Ohio State University, who said that he has piloted aircraft into Reagan National more than a hundred times.

Investigators are likely to focus on understanding why the helicopter entered the plane’s flight path and whether the air traffic controller handling both aircraft that night could have or should have done more to keep them apart.