The U.S. Federal Aviation Administration is indefinitely restricting helicopter flights near Washington Reagan National Airport after a deadly collision between an American Airlines regional jet and Army Black Hawk killed 67 people.

The National Transportation Safety Board said it was too soon to speculate the cause of the deadly crash. Skaters, parents, and coaches from the Skating Club of Boston were aboard the flight.

Wednesday's crash was the deadliest in the U.S. since Nov. 12, 2001, when an American Airlines flight slammed into a residential area of Belle Harbor, New York, just after takeoff from Kennedy Airport, killing all 260 people aboard and five people on the ground.

It appears that the first major air disaster in the U.S. since 2009 has occurred while the Federal Aviation Administration does not have a permanent leader.

U.S. President Donald Trump on Thursday said he had appointed a former senior aviation official as the acting head of the Federal Aviation Administration, a day after the deadliest U.S. air disaster in more than 20 years.