We will be catching a train to Fussen the same day we arrive at the Munich airport. I hear the airport has a train station. Will we be able to get to Fussen from the airport or will we have to take the S Baun to the central station and then get a train to Fussen? Would it be best to purchase train tickets to Fussen now or wait until we arrive in Munich? Do the trains get too full for a same-day purchase?
From the airport take S-Bahn to Hauptbahnhof and from there to Fussen. Purchase ticket in Munich. Check the schedule on Deutsche Bahn website.
S Baun??
It the S-Bahn - S for schnell or fast, Bahn for conveyance.
I wouldn't buy the ticket now. Wait and buy it at the S-Bahn station at the airport when you arrive. Get a Bayern-Ticket (31€ for two people). It covers the S-Bahn to the Munich Hbf, the train to Füssen, and the bus, if you need it, to Hohenschwangau (or any where else around Füssen).
I say don't buy the (Bayern-) ticket in advance, because once it is purchased online, it is only valid for the date specified. But since you are undoubtedly only arriving at the airport on that date, maybe advance purchase wouldn't be so bad. I might be easier online that figuring out the ticket machine the first time jetlagged.
Since the S-Bahn run starts at the airport it is unlikely the train will be full there. Anyway, if one train is full, there is another one in 10 minutes.
If you buy a Bayern ticket at the airport station (25 EUR 1st person, 6 EUR for each additional person up to 5 people) that will cover you to Fuessen. Buy out of a vending machine or pay 2 EUR extra for window service.
Starts after 9 am weekdays, anytime weekends. No such thing as trains too full. Maybe no seats left, but plenty of standing room.
There are two S-Bahn routes from the airport into town. One (S1) goes around to the west before coming into town; the other (S8) goes around to the east. One takes five minutes longer to get to the Hbf, but because each one leaves every 20 minutes, about 10 minutes apart, whichever one leaves next will get you to the Hbf first. No decision necessary; just leave on the next one. Pay attention to the map in the car. Know where you are so you can get off at the right station.