"Unplanned events" refers to unexpected or spontaneous occurrences or situations that were not previously scheduled, anticipated, or part of a plan. Full definition
There are plenty of unplanned events in life that can often times change an individual in the blink of an eye. (lauriegrengs.com)
The decrease had led to a dependency on precinct staff for unplanned events and special operations, as well as a reliance on overtime to meet law enforcement demands, according to the Council. (silive.com)
Nonuniformity could be intrinsic to the technology and / or result from unplanned events: E.g., a Lagrange point could keep reflectors in place, but not oriented; orientation would require active steering. (realclimate.org)