Faulty
or incomplete mental models are sometimes the cause of "mode"
errors. These occur when the user is either unsure of the mode that
the system is in or does not understand how the mode effects the
system.

Mode
error was attributed as the cause of the China Air Lines (CAL),
Airbus A300 crash in 1994. The pilot flying, new to the Airbus A300,
activated the "touch and go" mode, perhaps inadvertently.
In this mode, the aircraft was programmed to pull up during landing,
precedent to a "go around" aborted landing. The Captain
(non-flying pilot) noticed the autopilot was engaged and repeatedly
instructed the pilot to disengage it, but to no avail. The pilot
continued trying to force the aircraft nose down. The autopilot
performed as it was supposed to in this mode and forced the nose
up. Finally the pilot flying stopped pushing the yoke forward, and
the autopilot disengaged. The Captain took control, but it was too
late, the nose angle was too high, the aircraft stalled, fell 1,000
feet, striking the ground tail first.