Originally Posted by
Wombat1
In a few weeks I値l be taking a return flight to a Schengen country where I知 living for more than the 90-day tourist period. I hold a US passport and I have I have an unusual (but valid) set of entry documents for the country. I知 100% sure that I will be able to enter the country upon presentation of these documents but I知 concerned about convincing the airport staff of that as I値l need to do in order to get a boarding pass.
So long as your documents establish you may legally enter the country, UA document check is not going to flag that you plan to stay longer than the 90-day tourist period. For all they know you could have additional flights during that 90+ days that takes you to, e.g, the UK or another non-Schengen country. If anyone is going to be skeptical it's the border patrol on arrival, who might ask . . . but they'll be better positioned to acknowledge your documents allow you to stay longer. Assuming they check at all - for the same reasons.
The biggest issue I see you potentially having is leaving after 90 days, and the exit check may ask you why you overstayed the 90-day period. I trust you will have a good answer for that.