At one point during an annual flight evaluation for Capt. Rebecca M. Lobach on Jan. 29, her Army helicopter instructor paused their conversation to emphasize an aviation fundamental.

“The whole point” of emergency procedure checklists, Chief Warrant Officer 2 Andrew Loyd Eaves said as they flew their Black Hawk near Washington, D.C., “is ’cause we end up killing ourselves because we do something without confirming and verifying.”

His words, later revealed in a recovered cockpit voice recorder, were meant to be instructive. They turned out to be hauntingly predictive.

Less than an hour later, the helicopter crashed headlong into an American Airlines flight carrying 64 people on its way to Ronald Reagan National Airport, killing the two pilots, a fellow soldier who was riding in the back seat of the Black Hawk and everyone aboard the passenger jet.

As the two aircraft exploded into flames, an air traffic controller who had tried to guide the helicopter safely through the airspace soon saw he had failed. All the others’ lives had ended and his had changed forever.

The specific causes of the disaster are still under investigation, but enough has been revealed publicly to say that the events were set in motion by the failures of institutions. The Army’s unreliable technology in the aging helicopter may have given the pilots a misleading sense of their altitude. The Federal Aviation Administration’s short staffing meant that a single controller was doing two crucial jobs.

The agency, despite numerous warnings, never changed routes that allowed helicopters to fly perilously close to commercial airplanes landing at a certain runway. The Army used the busy airspace for training exercises at a time of night when commercial traffic could be heavy.

During the hearings, agency and Army officials defended their past decisions. An F.A.A. manager said that she had been aware of concerns about potential traffic jams between helicopters and planes near National Airport, but that protocols had prevented the agency from making certain requested warnings on its maps. An Army official said that the complex duties of Fort Belvoir’s helicopter crews made it difficult to schedule flights for the middle of the night.

But the disaster’s outcome was also particularly shaped by three people: the two pilots in the helicopter and the controller in the tower.

This week, investigators from the National Transportation Safety Board have released new evidence showing the difficulties those three key figures faced as a result of their institutions’ mistakes — and the decisions they made in the moments before the collision.

Early Difficulties

In 2021, Captain Lobach arrived for her first deployment at Fort Belvoir, the Army base south of Washington near Mount Vernon, Va., challenged by the demands of piloting there.

She was “eager to learn but initially had weak flying skills,” recalled a pilot who trained her upon her arrival, according to an N.T.S.B. report.

The 1980s-era Sikorsky Black Hawk she was flying there, known as the UH-60L, was “particularly taxing,” the pilot recalled, because Captain Lobach had used a newer model with more sophisticated cockpit instruments in flight school. In 2022, according to the report, she failed an annual flight test after having “lots of difficulties in the aircraft,” in the words of the pilot who was evaluating her.

But Captain Lobach was both studious and meticulous, according to friends and the N.T.S.B. report. She prepared carefully for her flights and soaked up advice, often grabbing a notebook whenever one of her instructors started talking, Austin Roth, a former Army instructor pilot who knew her at Fort Belvoir, recalled in a YouTube interview this year.

By 2023, she had passed her annual evaluation, and in 2024, she qualified to be a pilot in command, meaning she passed a comprehensive test of her flying skills. More senior pilots described her at that time as deeply knowledgeable and organized, the N.T.S.B. report notes.

By January, she was 28 years old and was running a platoon within her Fort Belvoir unit that was dedicated to petroleum oils and lubricants, critical fuels and other fluids for flying. She had logged 450 flight hours.

Learning to Fly

Mr. Eaves’s path to the Army had been indirect.

He had originally joined the Navy, where he served as an aviation crew member but did not fly aircraft, according to the N.T.S.B. report. He longed to, though. Years into his Navy service, he began a letter-writing campaign to the Army, his brother Forrest Eaves recalled to The New York Times, vowing to join up if the service would teach him to be an aviator.

The Army agreed, and in 2019 he arrived at Fort Belvoir, where he worked as a pilot and then as an instructor. Late in 2023, he transferred to an Army base in Honduras, where he gained additional experience in a different setting.

He was “very objective” as a teacher, recalled a senior officer who is noted in the N.T.S.B. report. A safety officer, also mentioned in the report, said he was “by the book.”

Mr. Roth, who had worked with Mr. Eaves, told The Times that he had a gentlemanly manner. Within their unit at the base, he added, Mr. Eaves would have been among the “more competent, more cautious, more safe” fliers. He was not showy or a braggart, Mr. Roth said.

Mr. Eaves, who was by then 39, returned to Fort Belvoir from Honduras in October. He had about 968 flight hours at that point. On any flight in which he was training a less experienced pilot, he would be considered the pilot in command, or the ultimate authority on the crew’s safety and effectiveness.

‘Rusty’ on the Controls

Much as she had improved over the years, some of Captain Lobach’s colleagues still considered her piloting skills to be subpar.

A fellow Army pilot who helped her practice for her final evaluation on Jan. 27 said she was “rusty” on the Black Hawk controls, according to the N.T.S.B. report, which showed that she had flown an average of less than five hours per month in the year before the test. He attributed it to a lack of recent flying — a common phenomenon among current Army aviators, who have seen a substantial reduction in cockpit hours since the end of wars in Iraq and Afghanistan.

That same week, Mr. Eaves, assigned to give her the annual flight exam, told his girlfriend that he feared Captain Lobach was unprepared for the flight, according to an N.T.S.B. interview document.

Captain Lobach, recalled the girlfriend, was described by Mr. Eaves as “not where she should be,” according to the document. It was the girlfriend’s impression, investigators said in the document, that Mr. Eaves “thought the other pilot was not grasping things they should have understood by that point in her flying career.”

Nonetheless, Mr. Eaves was professional and even jovial during the Jan. 29 flight, according to a transcript of the cockpit voice recorder.

He called Captain Lobach — his superior in rank — “ma’am” and made sure his crew chief, Staff Sgt. Ryan Austin O’Hara, was comfortable with the temperature in the back seat of the Black Hawk. He appeared to try to soothe Captain Lobach’s embarrassment over a directional mistake by joking that he was “all game” to blow by a town at low altitude but that they would have to make a “blood pact” not to discuss it with anyone later.

She appeared to have recognized the tongue-in-check suggestion, replying, “Nope, right.”

But the exam did not go smoothly.

More than an hour before the crash, during a portion of the flight with choppy winds, Mr. Eaves took the flight controls from her, according to the transcript.

At another point, when they were evidently practicing landing and other maneuvers on a rural airfield, she was forced to “go around” one landing area on short notice — a tactic that is often used when an aircraft cannot land safely, aviators told The Times. When Mr. Eaves asked her about the mistake, she blamed the height of her chair, according to the transcript.

She also erroneously turned left when she should have gone right to avoid winds, and turned northward toward Great Falls, Va., when she should have been heading south to return to the Army base, prompting Mr. Eaves to ask her where they were going, according to the transcript.

At one point, the transcript says, she described herself as “dizzy,” but quickly added that it was “not too bad.”

Little missteps might be relatively forgivable on a deserted airfield or at thousands of feet in elevation, where there is less traffic. But once the Black Hawk entered the Washington area’s airspace — known as Class B, the busiest grade — there was very little margin for error when problems emerged.

Traffic in Sight

As they flew along in Reagan National airspace, the pilots, each of whom had a set of altitude readings in front of their seat, voiced a difference in the helicopter’s height. Mr. Eaves told Captain Lobach twice to descend. But they never discussed the discrepancy in the altitude instruments, known as altimeters, and Captain Lobach flew the remainder of the route far too high.

The helicopter ultimately crashed into the jet at roughly 300 feet — higher than the maximum altitude of 200 feet in that part of the route.

“There is a tension within the crucial minutes between them over whether they’re flying at the correct altitude,” Jon-Claud Nix, a former Marine Corps helicopter instructor pilot, said in an interview with The Times after reviewing the transcript.

Mr. Nix, for instance, said that Captain Lobach announced an altitude of 300 feet and that Mr. Eaves replied by saying “roger, got you looking at four,” meaning his altimeter was placing her at 400 feet at roughly the same time.

Instead of discussing a fix to that differential, Mr. Eaves asked Captain Lobach to simply continue descending — which she did, but ultimately not enough.

‘A Little Overwhelmed’

The controller who had tried to guide the three-person crew safely back toward its Army base once had aspirations to be a professional pilot himself.

He was 36 years old, and loved the busy job of handling traffic at National Airport. “It feels like a video game,” he told investigators, a puzzle of planes and helicopters that needed to go different places at different speeds.

Investigators have not released his name. The F.A.A. said on Thursday that he was still on leave.

The controller had been on the job for five years, the last two-plus at National Airport. On this night, he was doing two jobs at once — guiding both planes and helicopters — in a tower where supervisors routinely overrode the rule that said those jobs were normally supposed to be handled separately until later in the evening.

On Thursday, as the N.T.S.B. conducted its second day of hearings into the crash, several witnesses described how that airport’s control tower was often understaffed, requiring controllers to push their limits just to keep up with traffic.

“We take pride in it, but I will say that at a certain point, it’s too much,” said Bryan Lehman, an F.A.A. official who runs another air traffic control center nearby. In the hearings, a different F.A.A. official said the agency had allotted 35 support positions to the D.C. region, but they did not appear to alleviate this tower’s problems.

On the night of the crash, as the Black Hawk helicopter approached, the controller was handling about 10 planes and helicopters, according to an F.A.A. official’s testimony.

The controller told investigators he felt briefly as though his workload might be too much.

“I was starting to become a little overwhelmed with the helicopters,” the controller told investigators later, according to an N.T.S.B. transcript of an interview two days after the crash.

He got a few helicopters through the airspace and on their way, and then the load felt more manageable. But even then, it was very busy.

He had planes lined up to depart from the airport’s most-used runway. So he shifted the incoming American Airlines flight to land on a lesser-used runway.

But that meant adding a small amount of extra risk.

Now, instead of sending the American Airlines plane on a path roughly parallel to the helicopter’s route, the controller was now sending it directly across the helicopter’s path, from east to west.

In the hearings, controllers said they had asked their bosses for the F.A.A. to move the busy helicopter route away from the approach path, to avoid danger where they intersected. But it never happened: An F.A.A. official who oversaw air traffic safety said in the hearings that the idea had never reached his level.

Later, when investigators asked the controller to reflect on the crash, the decision to reroute the incoming plane was the one he returned to: “I would have just kept them on [the original runway], that would have changed the whole situation.”

Even after shifting the plane’s course, the controller still had another out: telling the Black Hawk to wait upstream at Hains Point, the tip of a small island off the Potomac River’s east bank that was used as a holding spot for helicopters. He did not use it.

When investigators asked why, he said that sometimes keeping a helicopter in that spot created a backup with other helicopters wanting to use the same corridor.

Instead, he let the Black Hawk pilots proceed downriver toward the airport, warning them about the incoming plane. They were supposed to use “visual separation.” That meant it was up to Captain Lobach and Mr. Eaves to know where the plane was coming from, see it, let it pass and then fly safely behind it.

They told him they saw it.

Ninety seconds passed. In the tower, the controller dealt with another airplane taking off, and two other passing helicopters, recordings show.

Then he looked out of the tower, across the Potomac, and saw something concerning: The Army helicopter was “way closer” to the descending airliner than he had expected it to be, according to the interview transcript.

The controller called out to the Black Hawk again. “You have the C.R.J. in sight?” he asked, using an abbreviation for the regional jet.

Mr. Eaves said they did.

In Thursday’s hearing, officials from the F.A.A. and the Army said that the controller should have also notified the plane’s pilots of the nearby helicopter.

Crash investigators asked the controller about that, too.

At first, he was unable to finish his answer.

“I don’t think it would have made a difference honestly,” the transcript says. “That guy — I don’t — let m—”

“Would you like to take a break?” an investigator said.

“Yeah,” he said.

Later, when they returned, the controller indicated that he had not issued that warning because “there were other duty priorities going on at the time.”

Missed Opportunities

Earlier in the flight, Mr. Eaves had warned Captain Lobach about the need for caution. Confirm. Verify. But at the very end of the flight, Mr. Eaves seemed to not follow his own training.

He had told the controller he had the nearby traffic “in sight.” But in actuality, he seems not to have verified that the correct plane was in his sights, and he did not pause the helicopter in a safer spot such as Hains Point to assess the situation further.

Instead, he allowed Captain Lobach to carry forward, telling her to “kinda come left for me, ma’am,” because he surmised that was what the controller wanted, according to the N.T.S.B. transcript.

After a chain of institutional failures, oversights and missed opportunities, the pilots were exactly where they were not supposed to be: too high in the sky, too close to an active flight path, seconds away from hitting a plane they did not see.

She said “sure,” but it was too late.