The Senate Homeland Security Committee report said the U.S. Secret Service and U.S. Capitol Police didn't do enough to investigate the plans of the pilot, Doug Hughes, which were known as early as 2013.
The multiple agencies responsible for overseeing the restricted airspace had communication breakdowns as Hughes made his way from an airfield in southern Pennsylvania and into airspace near the Lincoln Memorial and over the National Mall before landing short of the Capitol on April 15.
Hughes is a former mailman from Ruskin, Florida, who said he was trying to protest the Citizens United ruling by the U.S. Supreme Court, which paved the way for super PACs and unlimited amounts of money to pour into political campaigns.
His flight went nearly undetected by radar, and law enforcement agencies had limited options to bring down his aircraft once he was in the air.
"Despite technological limitations, law enforcement officials had the opportunity to conduct further analysis of Mr. Hughes and his intentions two years before the gyrocopter incident occurred," said Sen. Ron Johnson, chairman of the Senate Homeland Security Committee.
Sen. Tom Carper, the top Democrat on the committee, said the incident "drew attention to gaps in security, and led to serious questions about the coordination among the agencies who work to protect the Capitol, the White House and the highly-restricted airspace above sensitive areas of Washington."
The Secret Service interviewed Hughes in 2013 after learning he had plans to fly a single-seat aircraft to the grounds of the U.S. Capitol or White House.
But despite indications he lied to investigators by claiming he didn't own a gyrocopter, and being contradicted by family members, the Secret Service office in Tampa closed its case. Hughes declined a second interview with agents without his lawyer being present, the report said.
Senate investigators said agents concluded Hughes posed no threat to officials protected by the Secret Service. The U.S. Capitol Police, which was told of the investigation, didn't conduct its own investigation and closed the matter as well.
On the morning of the flight, the agencies scrambled to react to information Hughes was en route, but they didn't coordinate, the report said.
The biggest issue remains limited technological capability to prevent another such flight. At times, the FAA said Hughes' aircraft appeared on radar to be bird or balloon, the report said. U.S. law enforcement agencies are still studying solutions, such as jamming equipment that could bring down drones and other small aircraft that violate sensitive airspace.
The Secret Service declined comment. The U.S. Capitol Police did not immediately return a request for comment.