The air traffic controllers on duty at Ronald Reagan National Airport on the night that a Black Hawk helicopter crashed into a commercial jet, killing 67 people, were never tested to determine if any of them had alcohol in their system at the time of the accident. And it took 18 hours before they were tested for drugs.

That was a break with the Federal Aviation Administration’s rules, witnesses told the National Transportation Safety Board during three days of public hearings into the Jan. 29 crash, noting that drug and alcohol testing should happen within two hours of a death or an incident that requires medical treatment off-site or causes substantial damage. The tests should never have happened more than eight hours after the accident, which occurred just before 8:48 p.m.

But instead of being tested, the controllers on shift were told they could go home at midnight, according to an N.T.S.B. report. Fifteen minutes later, agency officials determined that drug and alcohol testing was in order. But they didn’t notify the controllers until the following afternoon — missing the eight-hour window by several more hours.

“We had drifted out of our normal process,” Nick Fuller, the F.A.A.’s acting deputy chief operating officer for operations, said under questioning from Jennifer Homendy, the N.T.S.B. chairwoman, on Friday, explaining that the officials who would have been responsible for coordinating the drug test got busy trying to pull data and determine which controllers needed to be tested.

“The local controller may not have been the controller who issued the instruction,” Mr. Fuller continued, adding, “We have to listen to the tapes, do our investigation to determine who was involved in that specific incident and that’s who to test.”

Eventually, the whole team was tested for drug use, but not alcohol. Investigators have not accused any of the controllers of being under the influence.

Mr. Fuller said that since the accident, the F.A.A. had been training all of their on-call specialists to be snappier about administering alcohol and drug tests in the aftermath of a serious incident.

That didn’t satisfy members of the board. J. Todd Inman, a board member who previously worked at the Department of Transportation, said that the F.A.A. “had failed on other occasions to do the exact same thing.”

“It was something we were trying to address in 2018,” he said, recalling his time at the department. “Now, it’s seven years later and we’re saying, ‘Oh, we’re going to go back and rewrite it again.’ It shouldn’t have to be a continual process.”

“Do better,” he added.