I don't have any experience with separate PNRs but considering Olympic and Aegean are owned by the same company, codeshare extensively and have the same FFP, you should be able to check your bags through at Santorini. If you have status with Miles and Bonus, that would help. Since you mentioned that you have a SQ redemption, my guess is you have status with SQ or at least accumulate miles with them. If through checking is not possible, I doubt you'll be able to make the Paris flight. The Athens airport is not big, so once you arrive from Santorini, you can then exit to Baggage Claim in roughly 5 minutes, however, I never checked bags to Athens, so not sure how long it takes for them to come out. Furthermore, Aegean may have a cut off of when you can check bags, so that might be a problem as well. If you accomplish that, getting through security should be no issue - you can be in the gate area within 15 minutes or less. Ultimately, it may be possible if everything works in your favor but if it's important you be in Paris right after your flight lands, I wouldn't risk it. Also, not sure should you miss your Paris flight if Aegean will accommodate you on another one given it's a redemption booking through SQ. You may try to get in touch with SQ at that point to see if they can change you to another flight but Aegean most likely won't help in this situation. Now, if you can get your luggage checked in Santorini all the way to Paris, you should be just fine. Once you land in Athens, you'll be in the same area where your Paris flight will depart from, so all you need to do is find the departing gate and you can get there within 5 minutes, so plenty of time to make it. Keep in mind that Aegean/Olympic use parking stands a lot at Athens, so your Santorini flight might arrive away from the terminal and you will then be bused to the gates. Not sure if that's factored in to the flight time but as you suspect, this process might take at least 10 minutes - quite a valuable time on such a short connection, especially if you are not able to check your luggage all the way to Paris.