A computer implemented method of computing performance for an aircraft, comprises the steps of collecting data from a plurality of data sources comprising data sources of avionics type and external data sources of non-avionics type; processing the data collected in an electronic device of EFB or electronic flight bag type; and undertaking the performance computation. Developments describe the extraction of data from images or audio streams; the manipulation of data of alarm, INOP, aircraft status, air conditioning and anti-ice, runway, ATIS, meteorological and/or NOTAM type; the interfaces with an FPS or flight planning system and/or a CMS or centralized maintenance system. System aspects and software aspects are described.