If you are talking about Touring Plans.com, then yes. In the list of personalized plans, there should be a "delete" link to the right of the plan date. That's usually the 3rd line for the plan name and description.
I forgot to say "on the web". I only use the app when I am in the park. There's more that you can do with the web interface that you don't get with the app. I especially like the map for your plan. I haven't found that on the app.
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