A project manager cannot be proactive without an up-to-date and credible plan, i.e. without knowing what is going to happen on their project next week, next month, etc. This is serious. Not only because doing otherwise tells people you are an ineffective project manager but also because of the demoralising effect it has on team members.
There is no excuse for a project manager not to have a plan prepared (written down or in their head) for organising themselves first and foremost but also to make available to anyone who needs it.
If the company does not require a plan in a specific format, the project manager should propose one proactively. There are many templates and examples available so as not to invent one (everything a project manager needs has already been invented). The best format will be the one that meets the communication objectives set by the projects director. A Gantt Chart is usually the most appropriate but a list of outstanding tasks might suffice, or a list of deliverables, a list of risks, etc.
Lets not assume that planning is only done at the beginning of a project. Planning is useful at any stage and possibly most useful in the final weeks before completion when deliveries need to be formalised.
Of course, the best situation is one with good planning from the outset that has been agreed with those involved and the experts, starting with having a clear idea of who is sponsoring the project, who else is involved, what is the basis, deadline, budget, risks, scope, milestones, activities, costs, etc.
When a project manager who struggles every day to manage a crisis by improvising, responding to requests, etc. looks up and decides to plan ahead, we are reminded a little of Neo from the film Matrix when he decides to stop running and fight Mr Smith. Trinity asks Whats he doing? to which Morpheus replies He is starting to believe.
Our project manager would say something like: Thats enough improvisation. I plan my projects. On Monday, I will plan the activities for this week and then those for the week after .