It is not possible to delete plans in bulk mode by Advanced Roadmaps today's design, which leads to a lot of effort when a user must delete tens, hundreds, or thousands of plans manually.

It would be much easier if a bulk option could be added when comes to deleting plans.
That would lead to reducing time expending with scenarios where can be quite challenging to clean so many outdated plans, improving by that customer's experience with Jira in general.

Today's documentation:

• Creating and deleting plans

  Deleting a plan
  In your plan, click more (***) > Delete.