Rising temperatures could keep more flights from taking off on time

Airline passengers know to expect possible flight delays when weather forecasts call for thunderstorms, heavy snow or strong wind. The omens are less obvious on a hot summer day with clear skies.Yet extreme heat also disrupts flights and travel plans. On the hottest days, thinner air can make it harder for aircraft to get off the ground safely. Airlines may have to lighten the load by removing passengers or cargo, or carrying less fuel.The snag is well known at airports in desert climates around the world, from the U.S. Southwest to the Middle East. But even less extreme heat can create similar challenges at airports with higher elevations or shorter runways. Researchers say human-caused climate change could make such disruptions more common.With heat waves searing parts of the United Stat