ATC does not take appointments. Planes arrive early and late all the time. All ATC offers is _sequencing_ through protected airspaces. Your pilot is literally picking up their actual clearance on the ground right before engine start.
Planes can declare emergencies, they can divert to alternative locations, turn around for maintenance issues. And this is just IFR flights. VFR flights can take off, and once outside of controlled airspace, can just fly mostly however they want.
Your doctor takes appointments. That's a more apt analogy for what port appointments will create.
That’s actually not true for airlines, which are the better analogy here. For airline traffic airports have slots, which are basically appointments, attached to fixed flight schedules.
At the most congested airports slots are highly valuable, to the point where they’re often listed separately as part of an airline’s assets, and airlines will sometimes trade slots.
Many countries will fine airlines if they miss their slot time for reasons that aren’t related to emergencies or bad weather, as well as fine them for any other slot misuse such as hoarding, strategic cancellation, etc.
Now, sure, it’s not a case where if you miss the slot you can’t land or take off. The airport and ATC will always try to accommodate flights no matter what. But it usually means fairly substantial delays to avoid impacting on other take off, landing, and gate slots.
Slots have a very wide time range so thinking of them as "appointments" is entirely misleading.
Also airlines have been given waivers since the early 2000s because the FAA realized that they were simply operating empty "ghost flights" merely to keep their slots allocated to them. So we just give them waivers every year so they don't waste fuel on this stupidity.
The ATC/FAA model is entirely inappropriate for ports.
That’s not the case globally. Heathrow for instance has strict slot time ranges. As does Schiphol.
Neither the UK nor the Netherlands choose to not enforce slot misuse. We’re not talking only about the US and the FAA as examples here.
Whether it’s an appropriate model for ports and especially truck traffic at ports is a different topic, one I’m not qualified to speak on. I was just pointing out the misconception on how airline traffic at airports works and how it’s certainly not just a first-come, first-served ad hoc model.
Slots aren’t managed by ATC. They’re typically managed by the airport as there’s a whole host of facilities impacts to a slot, not just the airspace aspect.
If ATC does not take appointments, they do give appointments. Useful search term is “expect further clearance.” If all else (e.g. your radio) fails, you can plan to have that space reserved at the time indicated.
I’d argue, of course, that when you file a plan, you’re requesting an appointment.
Planes can declare emergencies, they can divert to alternative locations, turn around for maintenance issues. And this is just IFR flights. VFR flights can take off, and once outside of controlled airspace, can just fly mostly however they want.
Your doctor takes appointments. That's a more apt analogy for what port appointments will create.