Bleed air system refers to the air that is "bled" from the compressor stage of a turbine engine. The engine bleed air system directs hot bleed air to the intake of the compressor, to prevent ice accumulation on the front frame.

The use of engine anti-icing reduces engine performance partly, because the bleed air is taken off the side of the engine and partly because introducing warm air into the inlet reduces the mass flow.

Also, tapping air from the compressor reduces the mass flow through the engine. This increases the engine's operating temperature and reduces power output or thrust available, whilst specific fuel consumption increases.

As a result, the thrust reduction will affect negatively the power available, thus a greater take-off distance will be required.

Because of the bleed-air system effect on performance, it is advised not to be used during critical flight phases, such as take-off, approach and landing, unless it is necessary.