If you're staying in the non-Schengen part of the terminal and simply changing planes at FRA, I'm not sure if that counts as being *in* the Schengen region.
Posters in the Coronavirus and travel forum may able to provide better guidance.
Regarding the Schengen Travel Ban -> Even a 30 minute stay at Frankfurt Airport (airside non-Schengen) counts as a stay in the Schengen area.
OP is not admissable to the US until June 13.
TK staff at
Kayseri will conduct a very diligent document check for US-bound passengers. They will notice your travel pattern and that you have stayed in the Schengen area. And if the staff does not notice it in Kayseri, the gate checkpoint at Istanbul Airport will uncover that. Don't take the chance!
Who has issued your ticket? Lufthansa? What are the first three numbers of your ticket number?
Lufthansa allows rebooking on all fares (incl. restricted T). You just need to rebook before May 28 and pay the fare difference. Hence, I recommend you to push back your return flight to June 13.
https://www.lufthansa.com/de/en/exte...ooking-options
btw: You are also risking a denied boarding situation at BOS. You haven't told us anything about your citizenship + we have no info how you want to get from CAI to Kayseri. If Egypt requires an onward ticket as entry requirement, you won't be allowed to board your LH flight BOS-FRA. You technically have a roundtrip ticket, but your ticket is unfliable. LH contract staff at BOS will spot that immediately and flag you.
Last edited by warakorn; May 5, 2021 at 11:33 am