A refrigeration unit for an aircraft comprising: an evaporator that is configured to receive an airflow and a refrigerant and operatively arranged to transfer heat from the airflow to the refrigerant in order to evaporate at least some of the refrigerant and cool the airflow as the airflow travels from an inlet at an inlet side of the evaporator to an outlet at an outlet side of the evaporator, wherein, in use, the refrigerant travels from an input of the evaporator to an output of the evaporator, the outlet being for fluid communication with a compartment (102, 104) of the aircraft; a compressor that is configured to receive the refrigerant from the output of the evaporator and pressurize the refrigerant; a condenser that is configured to receive the refrigerant from the compressor and condense the refrigerant to liquid phase; one or more sensors operatively arranged for monitoring temperature of the airflow at the inlet side of the evaporator; a control unit operatively arranged to control operation of the refrigeration unit; characterised in that: the refrigeration unit comprises a heater positioned at the inlet side of the evaporator that is configured to heat the airflow before the airflow passes through the inlet of the evaporator; the control unit is configured to receive an altitude of the aircraft and the temperature of the airflow at the inlet side of the evaporator; and the control unit is configured to turn on the heater upon identification of the possible or likely formation of ice, based on a comparison of the temperature of the airflow at the inlet side of the evaporator and the freezing temperature of water at the current altitude of the aircraft. an evaporator that is configured to receive an airflow and a refrigerant and operatively arranged to transfer heat from the airflow to the refrigerant in order to evaporate at least some of the refrigerant and cool the airflow as the airflow travels from an inlet at an inlet side of the evaporator to an outlet at an outlet side of the evaporator, wherein, in use, the refrigerant travels from an input of the evaporator to an output of the evaporator, the outlet being for fluid communication with a compartment (102, 104) of the aircraft; a compressor that is configured to receive the refrigerant from the output of the evaporator and pressurize the refrigerant; a condenser that is configured to receive the refrigerant from the compressor and condense the refrigerant to liquid phase; one or more sensors operatively arranged for monitoring temperature of the airflow at the inlet side of the evaporator; a control unit operatively arranged to control operation of the refrigeration unit; characterised in that: the refrigeration unit comprises a heater positioned at the inlet side of the evaporator that is configured to heat the airflow before the airflow passes through the inlet of the evaporator; the control unit is configured to receive an altitude of the aircraft and the temperature of the airflow at the inlet side of the evaporator; and the control unit is configured to turn on the heater upon identification of the possible or likely formation of ice, based on a comparison of the temperature of the airflow at the inlet side of the evaporator and the freezing temperature of water at the current altitude of the aircraft. the refrigeration unit comprises a heater positioned at the inlet side of the evaporator that is configured to heat the airflow before the airflow passes through the inlet of the evaporator; the control unit is configured to receive an altitude of the aircraft and the temperature of the airflow at the inlet side of the evaporator; and the control unit is configured to turn on the heater upon identification of the possible or likely formation of ice, based on a comparison of the temperature of the airflow at the inlet side of the evaporator and the freezing temperature of water at the current altitude of the aircraft.