WASHINGTON — Model-aircraft hobbyists, research universities and commercial drone interests filed lawsuits Friday challenging a government directive that they say imposes tough new limits on the use of model aircraft and broadens the agency’s ban on commercial drone flights.

The three lawsuits ask the U.S. Court of Appeals for the District of Columbia to review the validity of the directive, which the Federal Aviation Administration issued in June. The agency said the directive is an attempt to clarify what is a model aircraft and the limitations on their operation.

The FAA has been working on regulations that would permit commercial drone flights in U.S. skies for more than 10 years, but the agency is at least months and possibly years away from issuing final rules to permit flights by small drones. Regulations for flights by larger drones are even further away.

Part of the agency’s challenge is to distinguish between planes flown by hobbyists and those used for commercial applications, a distinction that’s become harder to draw as the technology for model planes has grown more sophisticated.

A law passed by Congress in 2012 directed the FAA to issue regulations permitting commercial drone flights by the fall of 2015, but prohibited the agency from imposing new regulations on model aircraft.

The FAA directive is a backdoor imposition of new regulations on model-aircraft hobbyists and commercial drone operators without going through required federal procedures for creating new regulations, said Brendan Schulman, a New York attorney representing the groups that filed the lawsuits.

Federal procedures require an opportunity for public comment on proposed regulations and an analysis of the potential costs of the regulations versus the benefits.

“People who have been using these technologies for years in different ways are concerned that they are suddenly prohibited from doing so without having their voices heard, and without regard to the detrimental impact on the commercial drone industry,” he said.

Schulman said that hobbyists have been flying model aircraft nearly 100 years, but he knows of no instance in which a model aircraft has caused the crash of a manned plane or helicopter.

An FAA spokeswoman declined to comment on the lawsuits.

The lawsuits were filed by the Academy of Model Aeronautics, the Council on Governmental Relations and several commercial-drone and model-aircraft interests.