The Indian airline Vistara has its main hub at Indira Gandhi International Airport. The airline mainly operates domestic connections, even if they also offer some destinations in other parts of Asia and Europe. Vistara isn’t currently a part of any international airline alliance, but has codeshare agreements with major operators such as United Airlines and British Airways.
An airline hub is an airport where the airline has a heavy presence and normally some kind of headquarters. On the other hand, a focus city is a destination where the airline operates limited point-to-point routes. In these cities, the airline doesn’t necessarily need to have an office (even though this sometimes is the case). Many low-cost airlines don't use the definition 'hub' but instead define their main airports of operations as an operating base.
IATA Code: UK
ICAO Code: VTI