The government admitted it “owed a duty of care to plaintiffs, which it breached, thereby proximately causing the tragic accident” and that the pilots of the Army helicopter and regional jet “failed to maintain vigilance so as to see and avoid each other.”

The Justice Department said a Federal Aviation Administration air traffic controller also did not comply with an FAA order and as a result of both agencies conduct the United States was liable for damages.

The FAA declined to comment.

Robert Clifford, an attorney for the family of one of the victims of the crash that filed the suit, said the filing showed “the United States admits the Army’s responsibility for the needless loss of life in the crash … as well as the FAA’s failure to follow air traffic control procedure.”

Clifford added the “government, however, rightfully acknowledges that it is not the only entity responsible for this deadly crash, and, indeed, it asserts that its conduct is but one of several causes of the loss of life that January evening.”

American Airlines filed a separate motion to dismiss the lawsuit Wednesday, saying it was sympathetic to the families’ “desire to obtain redress for this tragedy” but the “proper legal recourse is not against American. It is against the United States government … The court should therefore dismiss American from this lawsuit.”

The FAA restricted helicopter flights in March after the National Transportation Safety Board said their presence posed an “intolerable risk” to civilian aircraft near Reagan National. In May, the FAA barred the Army from helicopter flights around the Pentagon after a close call that forced two civilian planes to abort landings.

On Wednesday, the US Senate unanimously passed legislation to tighten military helicopter safety rules.