Originally Posted by
supine
Not really. Frankfurt is not the problem for separate tickets, the main risk is the operator of the flight to Frankfurt denying you boarding because they insist on treating Germany as your destination and assessing you under those rules.
There was zero question at AA checkin that we were transit passengers. The separate ticket did not matter to them at all. It took them awhile to navigate the system and input our info but it was never a question if we would be able to do it.