A method of determining an inlet total air pressure of air at an air inlet of an aircraft engine, the method comprising: determining, at a computing device, a first parameter (P1IN) indicative of a first inlet total air pressure (P1IN) at the air inlet; executing, at the computing device, a sequence that includes: determining, at the computing device, a mass air flow (W1C) passing through the air inlet based on the first parameter (P1IN); determining, at the computing device, a Mach number of air passing through the air inlet based on the mass air flow (W1C); determining, at the computing device, a static air pressure at the air inlet; determining, at the computing device, an air pressure ratio (P1R/PS1E) based on the Mach number, the air pressure ratio (P1R/PS1E) defined as a revised inlet total air pressure (P1R) over an estimated static air pressure (PS1E) at the air inlet; generating, at the computing device, a subsequent parameter (P1R) indicative of the revised inlet total air pressure (P1R) based on the air pressure ratio (P1R/PS1E) and the static air pressure; and substituting, at the computing device, the subsequent parameter (P1R) for the first parameter (P1IN); executing, at the computing device, at least one additional instance of the sequence with the subsequent parameter (P1R); and outputting, at the computing device, the subsequent parameter (P1R) as the inlet total air pressure. determining, at a computing device, a first parameter (P1IN) indicative of a first inlet total air pressure (P1IN) at the air inlet; executing, at the computing device, a sequence that includes: determining, at the computing device, a mass air flow (W1C) passing through the air inlet based on the first parameter (P1IN); determining, at the computing device, a Mach number of air passing through the air inlet based on the mass air flow (W1C); determining, at the computing device, a static air pressure at the air inlet; determining, at the computing device, an air pressure ratio (P1R/PS1E) based on the Mach number, the air pressure ratio (P1R/PS1E) defined as a revised inlet total air pressure (P1R) over an estimated static air pressure (PS1E) at the air inlet; generating, at the computing device, a subsequent parameter (P1R) indicative of the revised inlet total air pressure (P1R) based on the air pressure ratio (P1R/PS1E) and the static air pressure; and substituting, at the computing device, the subsequent parameter (P1R) for the first parameter (P1IN); determining, at the computing device, a mass air flow (W1C) passing through the air inlet based on the first parameter (P1IN); determining, at the computing device, a Mach number of air passing through the air inlet based on the mass air flow (W1C); determining, at the computing device, a static air pressure at the air inlet; determining, at the computing device, an air pressure ratio (P1R/PS1E) based on the Mach number, the air pressure ratio (P1R/PS1E) defined as a revised inlet total air pressure (P1R) over an estimated static air pressure (PS1E) at the air inlet; generating, at the computing device, a subsequent parameter (P1R) indicative of the revised inlet total air pressure (P1R) based on the air pressure ratio (P1R/PS1E) and the static air pressure; and substituting, at the computing device, the subsequent parameter (P1R) for the first parameter (P1IN); executing, at the computing device, at least one additional instance of the sequence with the subsequent parameter (P1R); and outputting, at the computing device, the subsequent parameter (P1R) as the inlet total air pressure.