The airport manager is hereby directed and authorized to close the airport, or portions thereof, or suspend operations related to the landing, takeoff, or taxiing of aircraft during any period in which he determines that such operations, or their continuance, would be hazardous. Causes for such closure could include, but would not be limited to, adverse weather conditions, runway maintenance or repairs, runway obstacles, fire, aircraft or other accident. Any such closure shall be effective only during such time as there is placed at each end of each runway so closed a letter “X,” the arms of which are at least 20 feet long and two feet wide, and so colored as to contrast with the background or other surface. The airport manager shall immediately notify the local FAA facility advising of the closure.