An acoustic air data sensor for an aircraft, the acoustic air data sensor comprising: an acoustic transmitter located to transmit an acoustic signal through an airflow stagnation chamber; an acoustic receiver positioned at a distance from the acoustic transmitter to receive the acoustic signal transmitted by the acoustic transmitter through the airflow stagnation chamber; an acoustic signal generator that causes the acoustic transmitter to provide the acoustic signal; timing circuitry that determines a time of flight of the acoustic signal from the acoustic transmitter to the acoustic receiver; speed of sound determination circuitry that determines, based on the time of flight and the distance, a speed of sound (C 0) through air in the stagnation chamber; communication circuitry that outputs the speed of sound (C 0); characterized in that the acoustic air data sensor further comprises a temperature determination circuitry configured to determine, based on the determined speed of sound through the air in the stagnation chamber, a temperature of the air in the stagnation chamber, wherein: the airflow stagnation chamber is pneumatically connected to an exterior of the aircraft and configured to receive and stagnate airflow from the exterior of the aircraft; the temperature determination circuitry is configured to determine the temperature of the air in the stagnation chamber as proportional to a square of the determined speed of sound (C 0) through the air in the stagnation chamber; the acoustic air data sensor further comprises a humidity sensor located in the stagnation chamber to sense a relative humidity of the air in the stagnation chamber; and the temperature determination circuitry is configured to determine the temperature of the air in the stagnation chamber based on the determined speed of sound (C 0) through the air in the stagnation chamber and the relative humidity of the air in the stagnation chamber according to the formula: T = MC 0 2 γR where T is the total air temperature of the air in the stagnation chamber, M is the molecular mass of the air within stagnation chamber, C0 is the speed of sound measurement received from speed of sound determination circuitry, γ is the adiabatic constant of the air within stagnation chamber, and R is the universal gas constant (8.314 J/mol K). an acoustic transmitter located to transmit an acoustic signal through an airflow stagnation chamber; an acoustic receiver positioned at a distance from the acoustic transmitter to receive the acoustic signal transmitted by the acoustic transmitter through the airflow stagnation chamber; an acoustic signal generator that causes the acoustic transmitter to provide the acoustic signal; timing circuitry that determines a time of flight of the acoustic signal from the acoustic transmitter to the acoustic receiver; speed of sound determination circuitry that determines, based on the time of flight and the distance, a speed of sound (C 0) through air in the stagnation chamber; communication circuitry that outputs the speed of sound (C 0); characterized in that the acoustic air data sensor further comprises a temperature determination circuitry configured to determine, based on the determined speed of sound through the air in the stagnation chamber, a temperature of the air in the stagnation chamber, wherein: the airflow stagnation chamber is pneumatically connected to an exterior of the aircraft and configured to receive and stagnate airflow from the exterior of the aircraft; the temperature determination circuitry is configured to determine the temperature of the air in the stagnation chamber as proportional to a square of the determined speed of sound (C 0) through the air in the stagnation chamber; the acoustic air data sensor further comprises a humidity sensor located in the stagnation chamber to sense a relative humidity of the air in the stagnation chamber; and the temperature determination circuitry is configured to determine the temperature of the air in the stagnation chamber based on the determined speed of sound (C 0) through the air in the stagnation chamber and the relative humidity of the air in the stagnation chamber according to the formula: T = MC 0 2 γR the airflow stagnation chamber is pneumatically connected to an exterior of the aircraft and configured to receive and stagnate airflow from the exterior of the aircraft; the temperature determination circuitry is configured to determine the temperature of the air in the stagnation chamber as proportional to a square of the determined speed of sound (C 0) through the air in the stagnation chamber; the acoustic air data sensor further comprises a humidity sensor located in the stagnation chamber to sense a relative humidity of the air in the stagnation chamber; and the temperature determination circuitry is configured to determine the temperature of the air in the stagnation chamber based on the determined speed of sound (C 0) through the air in the stagnation chamber and the relative humidity of the air in the stagnation chamber according to the formula: T = MC 0 2 γR where T is the total air temperature of the air in the stagnation chamber, M is the molecular mass of the air within stagnation chamber, C0 is the speed of sound measurement received from speed of sound determination circuitry, γ is the adiabatic constant of the air within stagnation chamber, and R is the universal gas constant (8.314 J/mol K).