The Federal Aviation Administration announced Friday tighter restrictions on sightseeing flights over the Grand Canyon to reduce noise levels and improve safety.

The FAA said beginning next Sept. 22 sightseeing flights must remain outside four designated "flight free" zones and elsewhere fly at higher altitudes than before.Commercial sightseeing flights will have to remain outside the four restricted zones and no lower than 5,000 feet above sea level in the western section and 7,500 feet over the Boundary Ridge-Sunpai Point area of the park, the FAA said.

Special flight rules will apply to any pilot operating below 15,000 feet above sea level, the agency said.

The FAA last year designated certain airspace over the canyon for special flight rules. As part of the restrictions, flights also are prohibited in the inner gorge and below the canyon rim except in an emergency, the agency said.

Congress enacted legislation last August requiring the Interior Department to submit a flight restriction plan at the Grand Canyon. The FAA was required to implement the Interior Department plan unless the restrictions posed safety problems.

The FAA said the restrictions were not seen as posing safety problems and generally follow the Interior Department recommendations.