"There's things that could've been done in the last two months that still need to get done," he said, speaking to reporters following the hearing.
The National Transportation Safety Board's investigation into the incident is still ongoing, but the preliminary report highlighted over 15,000 close calls between helicopters and commercial aircraft near Ronald Reagan National Airport in just three years, with 85 incidents coming within 200 feet. As a result of that report, the Federal Aviation Administration moved to permanently restrict helicopter traffic near the airport's runways.
In an ironic turn of events, Lilley spent 20 years flying Black Hawk helicopters for the Army and has first-hand experience flying the routes near Reagan National Airport.
"I flew those routes hundreds of times, I knew that was a problem," Lilley said. "The days that I flew those routes we never ever had an aircraft on approach to [runway] 33 at the same time there was a helicopter on route four," he said. "I'm very disappointed that it was allowed to happen."
One of the key sticking points during the hearing centered on a critical air traffic transmission system known as automatic dependent surveillance-broadcast, or ADS-B, which broadcasts an aircraft's position, speed, direction, and other flight data.
Lawmakers during the hearing revealed most military helicopters do not transmit ADS-B data and commercial aircraft are only equipped to transmit data about their flights but do not receive data from other aircraft. The military has broad leeway over turning off the system for national security-sensitive missions and did not commit to changing its policy despite congressional pressure.
"We need to get the Army on board with some changes that need to be made and should have been made already by now," Lilley said.
Lilley said he will forever mourn his son's lost future. He was engaged and had planned on getting married this fall. He had earned his certification to fly commercial airplanes two years ago.
"This has been the hardest two months of my life," he said. "Sam was a terrific kid. We loved raising him and he had become a magnificent man. His career was really taking off. His fiance was just somebody that we really loved to be around.
"I was really looking forward to seeing what their children were going to turn out to be like because they wanted to start a family right away. It's not going to happen now. This is devastating," he continued.
The grieving father said he's committed to ensuring his son's legacy leads to meaningful aviation safety reforms, including updating air traffic control systems, increasing controller staffing, and implementing overdue procedural changes within the Army.
"What keeps us moving forward is that we're going to ensure that no other family has to go through what we're had to go through and the 66 other families that have had to go through," Lilley said. "The families are like-minded and getting change made. We're trying to do that while we grieve at the same time."
At the end of the hearing, families of the victims wearing blue ribbons gathered to speak with officials and lawmakers. Jennifer Homendy, chairwoman of NTSB, was seen comforting a crying woman.
Dailey Crafton, the brother of Casey Crafton, who died in the crash, said he was surprised to learn of all the lapses in safety protocols that led to the collision. His brother was on the flight and never made it home to his wife and three children.
"Specifically, even since the crash, certain safety measures that could have been simply implemented still have not been," Crafton said. "Accountability is still not being taken by parties who should be held responsible."
Crafton, who drove from his home in New York to Washington, said he believes the role of the ADS-B system is central to understanding the cause of the incident. He called Casey "the best human."
"He left everyone he met better, you know, for having known him, I'll miss him personally," he said. "As a friend, we had this great camaraderie, just being silly together was the way we connected," he explained.
He sees the restriction of helicopters at DCA as a "good start" but believes much more needs to be done.
"I'm glad that something's being done about it now, but you know, it's too little, too late for those of us who had family members on [the plane]," Crafton said. "No family should have to go through any of this."
CONGRESS REVIEWS DEADLY DC MIDAIR COLLISION: 'CLEARLY, SOMETHING WAS MISSED'
"We want safer skies and concrete ways that the responsible agencies are showing they're working for change," he said.