Using Velocity Silver to upgrade to Delta Comfort plus

[Simon Overall]

Hey all!

Quick question.

Flying Delta economy on Tuesday through to Atlanta.

I hold Velocity silver and know you can request an upgrade to Comfort plus at check in.

In people's experience, does this normally clear without issue, provided they have the seats?

 

[serfty]

You can generally select C+ seats at checkin.

 

[knagelli]

You can generally select C+ seats at checkin.

Does that mean I can only request Delta Comfort Plus upgrade only at the time of check-in and not in advance. I also have a Delta flight from LAX to SFO in Dec 2019 but was thinking it's better to be on waitlist sooner than later to check if I may be lucky but looks like I have to wait.