The U.S. government acknowledged Wednesday that mistakes by both an air traffic controller and an Army Black Hawk helicopter pilot contributed to last January’s deadly midair collision near the nation’s capital, which killed 67 people. The crash was the deadliest aviation disaster on American soil in more than 20 years.

In its response to the first lawsuit filed by a victim’s family, the government said it bears liability because the air traffic controller violated visual separation procedures and the Army helicopter pilots failed to maintain proper vigilance to see and avoid the passenger jet. However, the filing also suggested that other parties may share responsibility, including the airliner’s pilots and the airlines involved. The lawsuit names American Airlines and its regional partner, PSA Airlines, though both carriers have moved to dismiss the claims.