Upper surface (13) of an aerofoil (or rotor blade) is provided with nozzles or slots (14, 16) at leading portion (15) and trailing portion (17) to assist attachment of airflow by discharging gas towards trailing edge (11). Gas discharged may be heated, eg coming from rocket-type combustion chambers within the aerofoil. The aerofoil may be adjustable between high profile (as shown) and low profile (for supersonic flight) using jacks that pivot sections of upper surface (13) at leading and trailing edges (10-11).