We are flying BIO to CDG ( eventually to BOS), and we need to drop off rental car. What time should we arrive for 7:30 am flight on a Saturdy AM? I think this is a small airport, yes?

For European flights like this, the counter usually opens 1.5 hours before flight time in the morning. So, 6a will be fine.

The main issue is your rental car. The agency may not be open that early. You need to check with them first.

Thanks. It indicates that a drop box is available before 7 am so I think we'll be ok. I appreciate your pointing that out, though as this is the kind of detail that helps alot!

Well, do find out how far the rental car drop off is from the terminal. Coz you probably won't find a shuttle at 6a before the rental office opens. I don't know about BIO - it may be really close by, or may be not.

Thanks. I believe it is right at the airport not requiring a shuttle but I will check further. Has anyone rented a car there?

That airport is tiny! My experience at passport control was literally 1 or 2 people standing around between luggage claim and the exit asking what country you are from and waving you off!

90 min is plenty early for your flight, the car drop is in the main lot across the street, though if you are staying the last night in Bilbao, why not drop off in city center and take a taxi to the airport? It will save you a day's rate and parking fees...