You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Guam

Context:
Guam is served by the Antonio B. Won Pat International Airport, which is a hub for United Airlines. The island is outside the United States customs zone so Guam is responsible for establishing and operating its own customs and quarantine agency and jurisdiction. Therefore, the U.S. Customs and Border Protection only carries immigration (but not customs) functions. Since Guam is under federal immigration jurisdiction, passengers arriving directly from the United States skip immigration and proceed directly to Guam Customs and Quarantine.

Question:
What major airline resides at the airport?

United Airlines