WASHINGTON, Sept. 25 -- The U.S. government said Thursday it has granted regulatory exemptions to six aerial photo and video production companies, opening the door for the film and television industry to use drones for filming.

The U.S. government also determined that the drones, also known as unmanned aircraft systems (UAS), to be used in the proposed operations do not need a certificate of airworthiness issued by the Federal Aviation Administration (FAA), saying a study found that they do not pose a threat to national airspace users or national security.

"Today's announcement is a significant milestone in broadening commercial UAS use while ensuring we maintain our world-class safety record in all forms of flight," U.S. Transportation Secretary Anthony Foxx said in a statement.

"These companies are blazing a trail that others are already following, offering the promise of new advances in agriculture and utility safety and maintenance."

In their applications, the firms said the operators will hold private pilot certificates, keep the UAS within line of sight at all times and restrict flights to the so-called "sterile area," according to the FAA.

In granting the exemption, the agency said it accepted these safety conditions, but with limitations. For example, the UAS should be inspected before each flight and operations at night are prohibited.

The six companies are Astraeus Aerial, Aerial MOB LLC, HeliVideo Productions LLC, Pictorvision Inc., RC Pro Productions Consulting LLC dba Vortex Aerial, and Snaproll Media LLC.

The FAA said it has asked for additional information from Flying-Cam, Inc., a seventh aerial video company that filed for exemptions in June.

The agency also said it is considering 40 requests for exemptions from other commercial entities