A midair collision between an Army helicopter and a jetliner killed all 67 people aboard the two aircraft, officials said Thursday, as they scrutinized the actions of the military pilot in the country’s deadliest aviation disaster in almost a quarter century.

A jet carrying 60 passengers and four crew members collided Wednesday with an Army helicopter while landing at Ronald Reagan National Airport near Washington, prompting a large search-and-rescue operation in the nearby Potomac River.