Upvote:0
In general you can buy any train ticket for the full price (i.e. that of an flexible ticket) at the train station right before departure. For long distance trains (IC, ICE, EC, and a few other) booking in advance can give you a discount but you are not able to take another train.
Upvote:1
I would suggest you to buy it at the station. I traveled across Germany with a EuRail pass and within Germany it doesn't mandate any reservations. Keeping that in mind, I was always able to get a seat.
My parents traveled there last summer too and they although they had a EuRail pass, one of the members who they were traveling with didn't. They were able to purchase a ticket for him on the spot without any significant additional costs.
Why would I suggest that you buy it at the station? Simply because it's more convenient, I'd rather buy a ticket at the station for a train I'm sure I'll make, than make sure that I can make that one specific train which I have a ticket for.
In terms of prices, I'm fairly certain that buying in advance would get you a cheaper price, but it won't differ by much and it's certainly not worth the hassle.
I also tried looking up your specific train as per the information provided in the comments, but I don't seem to see an option using the IC either.
Upvote:5
Traveling from the Cologne/Bonn airport (Köln/Bonn Flughafen) to Aachen involves a change of train at the main station in Cologne (Köln Hbf). Between Cologne and Aachen, the service consists mostly of regional trains (RE), with two trains per hour off-peak, plus a few high-speed trains (ICE or Thalys). Between the airport and Cologne, there is a frequent S-Bahn (suburban) service, plus the occasional long-distance train. The total journey time is about 85min by S-Bahn plus RE. You can save about 20min if you catch a high-speed train, but there are only a handful connections a day, so it's not worth hoping for that if you don't know exactly when you'll be traveling.
The ticket price is 16.80€ by regional train (purchased any time before departure), 24€ by ICE (last-minute fare), 19€ by ICE with non-exchangeable reservation.
So my advice is to buy a ticket when you arrive at the airport, board the first S-Bahn to the main station and there board the first RE train to Aachen (it'll have Aachen as its last stop). If you really care to save a few minutes and the first connection happens to involve an ICE, decide whether you want to pay 7.20€ extra.