A high-lift system for an aircraft with a main wing and a slat that by way of an adjustment device is adjustable relative to the main wing to various adjustment states, with a gap resulting between the rear of the slat, which rear faces the main wing, and the main wing, where the size of the gap results from the adjustment state of the slat relative to the main wing, where in the interior of the slat an air guidance channel with at least one inlet and an outlet is formed, where the inlet is arranged at the rear, which faces the main wing, in order to influence the airflow in the gap.