I've got 45 minutes in Frankfurt to change planes from an intra-European flight to a flight leaving for the US. I have't transited in Frankfurt in years but I know its a huge airport. Lufthansa is selling the connection, so they must think its possible. Is it possible or insane? Does Lufthansa typically hold intercontinental flights if the worst happens?
It all depends on everyone being on time. Since you are checked through all you have to do is a gate change hopefully behind security. Given those two conditions, it would be doable. I don't know if Lufthansa would hold a flight for a delayed passenger.
Marcus, The shortest flight change I've had at Frankfurt was one hour, and that worked well although it was close. As you mentioned, if they booked a 45-minute layover, it must be a "legal connection". If both flights are with Lufthansa, it's possible they're in the same terminal and your arrival gate and departure gates may be very close. In the same situation, I'd check the FRA website and look for the arrival and departure times for the flights you'll be using. The gate numbers should be listed. Good luck!