The ambiguity effect is a cognitive bias where decision making is affected by a lack of information, or "ambiguity". The effect implies that people tend to select options for which the probability of a favorable outcome is known, over an option for which the probability of a favorable outcome is unknown. This could lead to someone choosing a higher risk option simply because it is a known risk.
Flight safety context
An example of the ambiguity effect is when a pilot decides to fly an approach in questionable weather rather than diverting to an alternate airport which may have better weather but may have other unknown issues.