Mandatory frequency airports are rare in the United States, one example being Ketchikan International Airport (14 CFR 93.151), but they are common in other countries such as Canada, Australia, the United Kingdom and Norway; often, an MF or MTAF airport is one with scheduled passenger service but insufficient traffic to support a control tower. If there is a flight service specialist monitoring the frequency, the specialist will give pilots advisories about traffic, weather, and surface conditions, and may relay IFR clearances from en route controllers, but cannot give clearances him- or herself.