This is a future goal of mine, not a problem I currently face. Hope that doesn't invalidate the question.
I really want to fly aboard the aircraft registered N123AA (this is only a dummy registration standing in for a variety of real registrations that I want to fly on). The airline that operates N123AA operates many aircraft of N123AA's type. These aircraft are cycled through a few routes, so each route is not necessarily flown by the same aircraft each day. That is, a flight from AAA to BBB might be flown by N123AA on Monday and N456BB on Tuesday (as is common). So if I were to simply book AAA-BBB with this airline, I couldn't be sure I'd fly on N123AA.
What I want to do instead is book a flight on N123AA on X date and go wherever it's flying that day! N123AA flies from my local airport in the US to a few major European cities (depending on the route), and I'd be glad to visit any of them (I don't need visas for any of the countries either).
I know I could get tail swapped on the day of the flight, especially since the airline operates lots of other aircraft of the same type. But odds are there would be no swap.
I use Flightradar24 and FlightAware, but they don't work for this purpose. When I search by registration, I can see at most 24 hours into the future, depending on if flight plans have been filed. There is no info on what flight N123AA will be assigned to days/weeks/months in the future.
I also tried to find patterns using these websites, e.g. if N123AA flies AAA-BBB on Mondays and Thursdays, but there doesn't seem to be a pattern.
Not a duplicate of this or this (both on aviation.SE). Those questions ask how to determine the registration of the aircraft that flew a particular route or flight number after the flight has been completed. I need to determine the registration before I book the flight.
There are also multiple questions on travel.SE asking how to figure out which aircraft type will fly a given route in the future. My question is about aircraft registration, so not a duplicate.
"But why?!" This aircraft is a piece of aviation history, a living legend, and I want to fly on it before it retires (it's still young, so I have time)!