Indira Gandhi International Airport — New Delhi, India

Scale defines DEL more than almost any other trait: it stands as India's busiest airport by a considerable margin and ranks among the highest-traffic facilities anywhere, reflecting the sheer size of the population it serves. Named after Indira Gandhi, the country's influential and controversial former prime minister, the airport expanded dramatically ahead of the 2010 Commonwealth Games with a huge new terminal that ranked, at opening, among the largest passenger buildings on Earth. Air India and IndiGo both run major hub operations from Delhi, feeding an extensive domestic network reaching deep into India's interior alongside long-haul routes to Europe, North America, and across Asia. Persistent winter fog has historically disrupted operations, prompting investment in low-visibility landing systems to keep traffic moving through northern India's foggy season.