Summer Heat and Takeoff Performance

Hot air is thinner, so aircraft produce less lift and engines produce less thrust. On very hot days, aircraft may need to take off with less weight, which can mean carrying fewer passengers, bags or fuel.

Why heat matters

Warm air has lower density. At a given speed, wings generate less lift, and engines get less air. The runway length needed for takeoff increases. This effect is worse at high-elevation airports and on short runways. Together these are called density altitude.

What airlines do

• Use more runway and more power if available.
• Limit takeoff weight, which may mean leaving some cargo or baggage behind or carrying less fuel for stopovers.
• Schedule heavy long-haul flights at cooler times of day where possible.

In Pakistan

Summer temperatures in the interior, including Sindh and southern Punjab, can be extreme. Heat also contributes to storms later in the day.

What you may notice

• Delays while performance calculations are updated.
• Occasional offloading of bags on heavy flights.
• Longer takeoff roll.

Check the weather

Airport weather pages show temperature; for example Karachi. See also how much fuel an airplane carries.

General information only, not legal or safety advice. Details change; check with your airline and the relevant authority. See our editorial policy.