The US Federal Aviation Administration (FAA) has doubled the maximum operating altitude for commercial and governmental unmanned aircraft systems (UAS) from 200ft to 400ft.

This is applicable to UAS weighing less than 55lb.

As per the new certificate of waiver or authorisation (COA) policy, the commercial drones are not allowed to fly in restricted airspace and other areas where the agency does not allow UAS operations.

Operators are also required to fly under daytime visual flight rules, keep the UAS within visual line of sight of the pilot, and stay certain distances away from airports or heliports.

"This is another milestone in our effort to change the traditional speed of government."

The agency expects its latest announcement to cut down the workload for COA applications for industry UAS operators, government agencies and the FAA’s Air Traffic Organization.

It is estimates that the need for individual COAs will reduce by 30% to 40%.

However, other provisions for an FAA authorisation such as registering the UAS and proper certification for pilots, still continue to apply.

FAA administrator Michael Huerta said: "This is another milestone in our effort to change the traditional speed of government.

"Expanding the authorised airspace for these operations means government and industry can carry out unmanned aircraft missions more quickly and with less red tape."

More than 406,000 people have so far registered their drones with the FAA.