Inverted flight - Is when the airplane flips over and flies with its underbelly pointed up. An inverted flight indicates a problem with the angle between the right and left wings.
A dihedral angle provides the airplane with stability, as both vectors of lift are pointing slightly inward. The anhedral angle causes every slight change in the roll angle to increase until the airplane is inverted. In this new inverted position the airplane has achieved a dihedral angle and is once again stable.
To correct an inverted flight make sure that your airplane wings form a dihedral angle.