Question: What low-cost airline headquartered in Tan Binh District, Ho Chi Minh City, Vietnam, has the second busiest airport in Vietnam with its hub?
Sentence (from "Noi Bai International Airport"): The airport is currently the main hub of the country's flag carrier Vietnam Airlines, as well as a major hub of low-cost carriers Vietjet Air and Jetstar Pacific.
Relevant evidence: Yes