Time for connecting flight

Just immigration I believe, with customs in Barcelona. But that's still tight, especially if you have to go through security again.

just passport control, then security. we made a one hour connection in Frankfurt just a few weeks ago, but on the return trip after a short leg in Europe. We just barely made it and I had scope out accommodations for the night in the event we missed our flight. Coming from the states on a 9 plus hour flight I really wouldn't be happy about the connection. If your flight is just 5% late you will not make it. and remember the big long haul aircraft take longer to get out of the plane. sorry.

Yes, flight delays are a big killer for connections, and seem to be pretty frequent on transatlantic flights. On our recent trip to France, our connecting flight from Philadelphia to Paris was reading "On Time" for hours before the flight, and in fact right up to the scheduled boarding time. Then suddenly it was announced that there was a problem with the plane, and we'd be getting a different plane at another gate. It meant unloading and reloading everything, plus servicing the new plane. In the end, the flight left an hour late, but arrived only half an hour late, and we had left plenty of time for our train connection. And then on our return, the flight left about 45 minutes late and we almost missed our connection in Philadelphia.

Minimum connecting time at FRA is 45 minutes. If you arrived late you would be put on the next flight, presuming you are on one ticket.

Assuming you are not on the last flight for the day and assuming the next flight has room. I spend more time when booking tickets finding the one with the best connections than any other issue, including cost. My rule (which I recently broke) is no less than 1.5 hours on short hops (and I prefer 2 hours) and a solid two hours on every other connection. Without Global Entry it would be 2.5 hours minimum when entering the US. What do I do with all the free time? I got a Priority Pass card so I sit in the private lounge and drink free booze and eat free cheese and crackers. Beats sitting in an airport for 6 hours waiting for the next connection or spending the night in frakfurt.

If it was the last flight of the day then you would get paid overnight accommodation. And if the delay was over 3 hours then the EU261 compensation kicks in as well, if you are on an EU carrier. What the OP hasn't mentioned is what airline is being used. Lufthansa actively expedites its connections and timetables them at the MCT; transfer between airlines might be a different matter. Having said all this, anyone who isn't comfortable with the possibility can book the later connection to start with.

RE: "Lufthansa actively expedites its connections"
That might spur me to fly Lufthansa next time if I can. USAir apparently doesn't. On our return from France a month ago, we had a connection in Philadelphia which originally didn't seem like it would be a problem, but our flight from Paris was a little late. But it still seemed like we'd be fine after getting through customs and immigration and transferring baggage. Then when we got to security for all connecting international to domestic flights, it was a madhouse. There was someone there who might have been a US Air employee, but all he was interested in doing was making sure any of the few First Class passengers could skip the line. No attempt was made to help people with close connections. One traveler told this man he had only 30 minutes to make his flight, and the guy said: "You should be fine." He wouldn't have been, but other travelers told him to move to the front. We had almost an hour, and we only made our flight because I took matters into my own hands and asked TSA people for help. They were very accomodating, and other passengers also were understanding. Otherwise, we might still be in Philadelphia.

What Lufthansa will do for example is transfer people from plane to plane by car across the apron - although in the case of the OP this wouldn't happen as immigration is needed. I can recall being taken in a similar manner by American Airlines in JFK - but that was many years ago.

My last flight a few weeks ago had a 50 minute lay over in Frakfurt. It was Lufthansa. The plane parked on the apron right on time. They brought the bus out for us. Took forever to get the stairs in place and open the door. Bus had to stop for crossing aircraft traffic. By the time we got to the terminal we had 30 minutes to flight time. We ran to the Z gates (heading home to the states) and did all the security stuff. Fortunately our plane left 10 minutes late and everything was okay. I needed to work the next day so spending the night wasn't a good option but I was prepared if necessary. On the way over our Lufthansa flight from Houston to Frankfurt was about an hour late arriving in Frankfurt. No problem because I had a two hour layover. Missing that connection would have meant one day of vacation lost. Still not a good option.