The head of the Federal Aviation Administration has told Congress that the agency must do more to ensure flying remains safe after a midair collision over Washington, D.C., that killed 67 people.

The agency said it’s taking steps to lessen the risk of collisions, but lawmakers say too many gaps remain — and place part of the blame on the military.

Investigators have found that the Federal Aviation Administration had data showing the risk of a crash before the midair collision at Reagan National Airport.