London Heathrow, which handles over 60 million international passengers annually, is the largest airport in the UK.

London Heathrow (LHR) is significantly bigger and busier than London Stansted (STN) by almost every metric. Heathrow is the UK's primary international hub, covering approximately 12.3 square kilometers (4.7 sq miles) with four active passenger terminals and two major runways. In contrast, Stansted covers about 11 square kilometers and operates out of a single main passenger terminal. In terms of passenger volume, Heathrow remains the giant, handling over 80 million passengers annually in 2026, while Stansted typically handles around 28 million, focusing primarily on low-cost carriers like Ryanair. While Stansted's single-terminal layout makes it feel more compact and easier to navigate for European hops, Heathrow's vast infrastructure is required to support its role as a global gateway for premium, long-haul, and multi-airline alliance traffic.