I was on a flight this week (DEN-MSP) where NONE of the lavs were operational. And for some reason the seatbelt sign stayed on for the entire flight even though it was smooth as silk

I really don't think they would have dispatched the a/c knowing all the lavs were inop, but this flight was completely screwed up from the get go, so I have to wonder:

A/C was there (I assume all night).

Agents said they were waiting on the F/A's but no reason or time estimate (who I assume were there all night).

10 minutes before departure they show up (in no hurry with their frozen lattes).

We board at departure time, mechanic doing paperwork in the jetway and catering just now showing up.

No attempt to get people to sit down, several people standing, musical chairs, etc.

Finally leave about 25 minutes late, never any explanation why.

Then no lavs...

DL was not ready to operate this flight.