I am flying from IAD-KWI on United and then Lufthansa.

The IAD-FRA leaves on Thursday night, the FRA-KWI on Friday afternoon.

I am a 1K upgrading using a paper SWU.

I understand you can only upgrade "on the day of departure," according to the website rules.

My question is do I have to wait until I get to FRA to request the upgrade, or can I do it at Dulles?

Thanks....