London Heathrow Airport (LHR) operates with two main parallel runways. The Northern Runway (09L/27R) is the longer of the two, measuring 3,902 meters (12,802 feet) in length. The Southern Runway (09R/27L) is slightly shorter, measuring 3,660 meters (12,008 feet). Both runways are 50 meters wide and constructed of grooved asphalt to handle the world's heaviest aircraft, including the Airbus A380 and Boeing 777-9. These lengths are designed to allow for "heavy" takeoffs bound for long-haul destinations like Singapore or Los Angeles, which require significant runway distance when fully fueled. In 2026, Heathrow continues to use a "runway alternation" system to provide noise relief to local residents, switching which runway is used for landings and takeoffs at 3:00 PM daily. Discussions regarding a proposed Third Runway (Northwest Runway) continue in 2026; if built, it is expected to be approximately 3,500 meters long, though it remains one of the most complex and debated infrastructure projects in UK aviation history due to environmental and noise concerns.