The Florida postal worker who landed a gyrocopter on the West Lawn of the U.S. Capitol last month was indicted Wednesday by a federal grand jury in Washington on six felony and misdemeanor charges punishable by up to 9 1/2 years in prison, prosecutors announced.

Douglas Hughes, 61, of Ruskin, Fla., was arrested immediately after the April 15 incident and charged in a police complaint with a felony — violating registration requirements involving an aircraft — and released.

The indictment includes that charge, another felony count of operating without an airman certificate, three misdemeanor counts of violating national defense airspace and one misdemeanor count of operating a vehicle falsely labeled as a postal carrier, according to the U.S. Attorney’s office for the District of Columbia.

The indictment also seeks forfeiture of the gyrocopter, which was seized.

U.S. Capitol Police Chief Kim Dine leaves after testifying on Capitol Hill on May 20, 2015, before a House Administration Committee hearing to discuss safety concerns after a gyrocopter illegally landed on the U.S. Capitol grounds. (Andrew Harnik/AP)

Hughes’s attorney, Assistant Federal Public Defender Tony W. Miles, could not immediately be reached for comment. However, a publicist said Hughes plans to comment after his arraignment, which is scheduled for Thursday afternoon in U.S. District Court for the District of Columbia.

Wearing a letter carrier’s uniform, Hughes flew from Gettysburg, Pa., to Washington at low-altitude in a miniaturized helicopter. He said he was protesting campaign finance laws, but the broad-daylight stunt drew more attention for how his flight through Washington’s highly restricted airspace apparently went undetected by authorities.

“Mr. Hughes’s gyrocopter appeared on our radar as one of those small dots, indistinguishable from all other non-aircraft” such as birds, balloons or moving weather systems, Michael Huerta of the Federal Aviation Administration told a House panel April 29.

Last year, Hughes contacted his hometown newspaper, the Tampa Bay Times, and said that he planned to carry protest letters addressed to every member of Congress aboard his ultralight craft.

In the letters, Hughes declared “a voter’s rebellion” over the “corruption” of the electoral process by rich special-interest groups, decrying the Supreme Court’s 2010 ruling in Citizens United v. Federal Election Commission, which struck down limits on campaign donations by corporations and unions.

According to prosecutors, Hughes flew through three no-fly zones: One called Prohibited Area 56A and surrounding the White House spans the length of the Mall from the Lincoln Memorial to east of the Capitol and from Independence Avenue to K Street; a 15-mile-radius Flight Restricted Zone surrounding the nation’s capital; and a roughly 60-mile-radius Special Flight Rules Area that envelops the region’s three major airports.

Investigators said Hughes does not have an airman certificate — commonly calle a pilot’s license — or aircraft registration, and that his aircraft bore the logo and emblem of the United States Postal Service without authorization.

U.S. Magistrate Judge Deborah A. Robinson freed Hughes on personal recognizance and placed him under home detention on April 16. He was ordered to stay away from the Capitol, the White House and nearby areas and also was barred from operating any aircraft.