Display of the FUEL BAL messages may indicate an imbalance exceeding ___________ pounds for more than two minutes between the left and right fuel tanks, or a failure of the autobalance system.

The correct answer is 30 pounds. The FUEL BAL messages' display indicates that there is an imbalance in fuel levels between the left and right tanks that exceeds a critical threshold, which is 30 pounds, for more than two minutes. This message serves as a crucial alarm to pilots, alerting them to either a significant fuel imbalance that could affect aircraft performance or a potential failure in the autobalance system that normally helps manage fuel distribution. Understanding this threshold is vital for maintaining safety and ensuring that the aircraft operates efficiently.