Aviation is one of the most carbon-intensive activities a human can undertake, accounting for approximately 2.5% of global CO2 emissions and nearly 4% of total "global warming impact" when non-CO2 effects like contrails are included. A single round-trip flight from London to New York generates about 1.6 tonnes of CO2 per passenger—which is more than many people in developing nations produce in an entire year. The environmental impact is particularly high because emissions are released directly into the upper atmosphere, where they have a more potent greenhouse effect. In 2026, the industry is under intense pressure to decarbonize through the use of Sustainable Aviation Fuel (SAF) and the development of electric or hydrogen-powered regional planes, but these technologies currently only account for a tiny fraction of total fuel burn. Furthermore, "radiative forcing" from high-altitude contrails can trap heat even more effectively than CO2 alone. While modern planes are about 20% more fuel-efficient than those from a decade ago, the sheer volume of global air traffic continues to grow, making aviation a primary target for climate activists and a major challenge for achieving "Net Zero" targets by mid-century.