Edward Snowden, former CIA employee and whistleblower, recently released a document that revealed the National Security Agency (NSA) launched a sophisticated spy balloon, Hover Hammer, from “an airfield near Solomons Island” in Maryland.

The surveillance balloon was not similar to the ones that the Army tested at the Aberdeen Proving Ground (APG) near Aberdeen, Maryland. In 2015, one of the balloons broke away from its moorings and crashed somewhere in Pennsylvania, so funding was cut.According to an internal 2004 newsletter, the NSA rigged an airship that was 62-feet in length with gear to gather information about shipping. There were also plans to utilize the balloons for eavesdropping missions.

In 2013, Snowden was employed with the NSA, when he vanished, with a stash of classified files that detailed the agency’s global spying operations. Snowden eventually turned the classified files over to journalists.

The 2004 newsletter supplies only a few details about the balloon tests. However, the document does provide clues of expansion plans for utilizing the balloons to gather information.

“It’s got dual airbags, three engines and one of the most sophisticated audio systems around,” the post reads. “No, it’s not the latest sports car from Europe – It’s Hover Hammer, a steerable airship that may become one of the [multi-intelligence] platforms of the future.”

The airfield the spy balloon was launched from was probably Naval Air Station Patuxent River.

In recent years, the military has utilized balloons extensively to carry out intelligence gathering missions. It has not been determined whether the balloons are still operating in American skies.

The balloon tests at APG were intended for determining whether radar assemblies installed on blimps 243-feet in length could be sent up into the air and utilized to detect cruise missiles being launched at the East Coast and coordinate with air defenses.

Civil liberties activists became concerned, because the balloons utilized powerful cameras that could be utilized to spy on people. The Army responded by saying it had no interest in spying on people.

The Baltimore City Police Department recently partnered with Persistent Surveillance Systems to launch a program that utilizes special plans, with cameras to watch people from the air. The secret trial program was designed to track criminal suspects, according to city officials.