An aircraft leading edge ice protection system. The system includes: a thermoelectric heater mat (10) attachable to a leading edge component of an aircraft, the heater mat comprising: an electrically resistive heater element (12, 22) embedded in a thermoplastic layer (16, 26, 28), the thermoplastic layer having a first surface; and a first adhesive (20) receiving layer (18) located on a surface of the thermoplastic layer. A method of making an aircraft leading edge ice protection system, the method comprising: making a thermoelectric heater mat by embedding an electrically resistive heater element in a thermoplastic layer, the thermoplastic layer having a first surface; and locating a first adhesive receiving layer on a surface of the thermoplastic layer.