What could cause erratic or inaccurate indications in flight instruments?

Erratic or inaccurate indications in flight instruments can primarily stem from contamination, moisture, or air leaks. Flight instruments rely on precise measurements and calibrations to provide accurate data on the aircraft's performance and environment. Contamination, such as dirt or debris, can obstruct sensors or affect the calibration, leading to faulty readings. Moisture can interfere with electronic components or pressure systems, causing inaccurate instrument displays. Air leaks can disrupt the pressure systems critical for instruments like altimeters and airspeed indicators, further contributing to erratic behavior.

While excessive fuel weight and improper loading of passengers can affect the aircraft's center of gravity and overall performance, they do not directly impact the accuracy of the flight instruments themselves. External weather conditions, although they can influence flight performance, do not inherently cause the instruments to provide erratic readings. Thus, contamination, moisture, and air leaks are the key factors that can lead to such inaccuracies in instrument indications.