Originally Posted by ATOBTTR

IROPs = "Irregular Operations", i.e. delays/cancelations, etc. that drive misconnects and reroutes. The risk here is lets say your OTP-AMS or AMS-SEA leg is canceled or delayed. The airline is under no obligation to get you to SEA as that's not your final ticketed destination, it's technically SFO. So they could try to reroute you on say OTP-CDG-SFO or OTP-AMS-SFO or OTP-AMS-ATL-SFO or something that doesn't go through SEA at all. Of course, most airlines are pretty flexible in IROPs and you could probably play some games to get a more reasonable option. "Oh, AMS-SEA isn't available - well my final destination is about halfway between SFO and PDX - can you rebook me on AMS-PDX?" (where you're at least closer to SEA - an easy train ride or drive up to Seattle). "Oh, it's fine if you rebook on an option with an overnight in SEA - I have family I can stay with". Or suggest OTP-CDG-SEA-SFO. If you know your options and don't raise too much of a stink, you can really minimize the risk and still find something to/through/near SEA that works. Just do understand the risks involved with this option.

PS: I just realized this was your first post so welcome to FT.