Hi stevessg , thanks for your question! Yes, frontline users can access premium plans created by users with premium licenses. They would be able to edit and modify the plan, but would need a premium license in order to see and use premium features (e.g. Gantt charts, Goals view, sprints). More info on this here: https://techcommunity.microsoft.com/t5/planner-blog/enhanced-collaboration-in-project-for-the-web-with-your/ba-p/4076623. I hope this helps!