Issue: The GPS ALT value displayed on the DATA/GPS MONITOR page changes when the BARO/QNH setting is adjusted. Steps to reproduce: Spawn on the ground at any airport and allow the aircraft to finish alignment. Open MCDU → DATA → GPS MONITOR. Note the displayed GPS ALT. Change the BARO/QNH setting by a significant amount (e.g. ±20–30 hPa). Observe the GPS ALT value. Observed behavior: The displayed GPS ALT changes as the BARO setting is changed. Expected behavior: GPS ALT should represent the GNSS-derived altitude and therefore should remain essentially independent of the selected BARO/QNH. Minor fluctuations due to GNSS accuracy are expected, but changing the altimeter setting should not systematically alter the displayed GPS altitude. Additional information: The same behavior has been observed on the A330, A310 and A340, suggesting it may be common to the shared avionics implementation rather than being aircraft-specific.