My frequent miles are getting me as far as Frankfurt where I will have a three hour layover before I head off on Swiss Air into Hungary. Planning on only carry on; are Customs & airport difficult to navigate in Frankfurt?
FRA is a big airport with multiple concourses, but I have never found it difficult to navigate, particularly if you are staying in one terminal. If your luggage is checked through to Hungary, you won't even have to go through customs in Frankfurt. Since you are entering the Schengen zone, you will have to go through Immigration, but I don't think that has ever taken me more than about 15 minutes. If you are coming in on Lufthansa, it shares the same terminal (#1) with SwissAir.
Frankfurt is huge, but not particularly difficult. You have to go through passport control and maybe another security area. Three hours is enough time, but you want to go to your gate area (if I recall correctly, it's a lounging area and exact gates are given about 20 minutes before boarding) I could foresee issues if you booked each flight totally separately since you may need to get a boarding pass in Frankfurt. Also, if you have a delay on your incoming flight, Swiss Air won't know you are flying in. It should work fine ok with just a carry-on, but if you didn't book the flights together, if you checked bags you would have to pick up luggage and re-check which could take a very long time. I would look up an airport map online if you find you might need to get a boarding pass once you arrive - look for a Swiss Air service desk or transfer station or something for Star Alliance.
Andrea, Although FRA is a huge airport (one of the largest in Europe), I haven't had any significant problems in navigating my way around, or getting to connecting flights. A good example is the experience I had this year. When I purchased my tickets, I noticed that I had ONE HOUR after arrival in FRA to make a connecting flight to Rome. I questioned the Travel Agent and she checked with the airline. They said that was a "legal connection". I still wasn't completely convinced about the one-hour connecting time, so a short time before my flight landed in Frankfurt I expressed my concerns to the Flight Attendant. He said, "that won't be a problem in Germany, but don't stop for coffee". He was absolutely right! Fortunately, I chose a seat a few rows behind "business class", so I was able to disembark fairly quickly (right after all the "rich folks"). It was a quick trip through Immigration for a "stamp" on the Passport, and then through one of the quickest and most efficient security lines I've ever encountered. The entire process took fifteen minutes and I got to the departure gate for my Rome flight just prior to the "general boarding" announcement. One other advantage that helped in my case was the fact that all my flights were arranged via Star Alliance partners, so I didn't have to worry about my checked luggage. It was waiting for me in Rome (although that's another story). Happy travels!
As others have said, you'll have to go through immigration (passport control). I've sailed through on some days, sat in a line for an hour on others. There's not really any customs to go through, especially as you won't be picking up your bags. You will have to go through at least one security check before getting on your next flight. We had to go through 2 connecting to Dublin last year. But, on that trip, even with immigration and 2 security checks, we made our flight with only and hour and 15 minute layover. It was tight, but we made it.
For the last 5-6 years, I have always landed in Frankfurt and departed from Frankfurt to come home to the USA. I use this airport because it is efficient and the security staff, and passport control staff are also efficient. I have always used carry on luggage during this time and have never had trouble going through these areas quickly. However, I do remember a time when I had to wait about 15 minutes in the passport control line going into Germany and sometimes the security check point line can be lengthy. However, even in the security process it usually goes quickly. I really don't think you will use all 3 hours to continue on your trip. I have always used American Airlines so I am not sure which concourse you will come into and go to for Swiss Air. Have a great trip.