Given the question: Information: - Zurich Airport, also known as Kloten Airport, is the largest international airport of Switzerland and the principal hub of Swiss International Air Lines. It serves Zurich, Switzerland's largest city, and, with its surface transport links, much of the rest of the country. The airport is located north of central Zurich, in the municipalities of Kloten, Rumlang, Oberglatt, Winkel and Opfikon, all of which are within the canton of Zurich. - An international airport is an airport that offers customs and immigration facilities for passengers travelling between countries. International airports are typically larger than domestic airports and often feature longer runways and facilities to accommodate the heavier aircraft commonly used for international and intercontinental travel. International airports often also host domestic flights. Some, such as Frankfurt Airport in Germany are very large; others such as Fa'a' International Airport in Tahiti, are quite small. - Swiss International Air Lines AG (short Swiss, stylized as SWISS) is the flag carrier airline of Switzerland operating scheduled services in Europe and to North America, South America, Africa and Asia. Its main hub is Zurich Airport, with a focus city operation at Geneva Airport. The airline was formed after the 2001 bankruptcy of Swissair, Switzerland's former flag carrier. - Helvetic Airways is a Swiss airline based at Zurich Airport . It operates flights to destinations in Europe and Northern Africa , mainly leisure markets , but also to business destinations on its own behalf as well as scheduled flights on behalf of Swiss International Air Lines using their fleet of Embraer 190s and Fokker 100s . Given the information, choose the subject and object entities that have the relation of 'airline hub'.
The answer is:
helvetic airways , zurich airport