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:
Raleigh,_North_Carolina

Context:
Raleigh-Durham International Airport, the region's primary airport and the second-largest in North Carolina, located northwest of downtown Raleigh via Interstate-40 between Raleigh and Durham, serves the city and greater Research Triangle metropolitan region, as well as much of eastern North Carolina. The airport offers service to more than 35 domestic and international destinations and serves approximately 10 million passengers a year. The airport also offers facilities for cargo and general aviation. The airport authority tripled the size of its Terminal 2 (formerly Terminal C) in January 2011.

Question:
What are there 10 million of each year at the airport?

passengers