A system comprising: a first multi-function probe, MFP , comprising a first plurality of pressure sensing ports for sensing pressure of an oncoming airflow about an aircraft exterior, the first MFP , having a first electronics channel of the first MFP ; and an inertial reference unit, IRU , comprising a plurality of inertial sensors for sensing inertial data of the aircraft; wherein the IRU and the first electronics channel of the first MFP are electrically coupled to form a first air data system providing first aircraft air data parameter outputs; and a second MFP comprising a second plurality of pressure sensing ports for sensing pressure of an oncoming airflow about an aircraft exterior; and a third MFP comprising a third plurality of pressure sensing ports for sensing the pressure of the oncoming airflow about the aircraft exterior; wherein the second MFP has a first electronics channel of the second MFP and a second electronics channel of the second MFP ; and wherein the third MFP has a first electronics channel of the third MFP and a second electronics channel of the third MFP ; characterised in that the first electronics channel of the second MFP is electrically coupled with the second electronics channel of the third MFP to form a second air data system providing second aircraft air data parameter outputs; and wherein the second electronics channel of the second MFP is electrically coupled with the first electronics channel of the third MFP to form a third air data system providing third aircraft air data parameter outputs; wherein the first air data system, the second air data system, and the third air data system are independent and dissimilar. a first multi-function probe, MFP , comprising a first plurality of pressure sensing ports for sensing pressure of an oncoming airflow about an aircraft exterior, the first MFP , having a first electronics channel of the first MFP ; and an inertial reference unit, IRU , comprising a plurality of inertial sensors for sensing inertial data of the aircraft; wherein the IRU and the first electronics channel of the first MFP are electrically coupled to form a first air data system providing first aircraft air data parameter outputs; and a second MFP comprising a second plurality of pressure sensing ports for sensing pressure of an oncoming airflow about an aircraft exterior; and a third MFP comprising a third plurality of pressure sensing ports for sensing the pressure of the oncoming airflow about the aircraft exterior; wherein the second MFP has a first electronics channel of the second MFP and a second electronics channel of the second MFP ; and wherein the third MFP has a first electronics channel of the third MFP and a second electronics channel of the third MFP ; characterised in that the first electronics channel of the second MFP is electrically coupled with the second electronics channel of the third MFP to form a second air data system providing second aircraft air data parameter outputs; and wherein the second electronics channel of the second MFP is electrically coupled with the first electronics channel of the third MFP to form a third air data system providing third aircraft air data parameter outputs; wherein the first air data system, the second air data system, and the third air data system are independent and dissimilar. <EOS>