Saturday noon flight, 3 hours?

Departing tomorrow unfortunately. Our flight is at 12:15pm with Air Transat. Checked in online but have to drop bags and pay the fees. Once that is done am I free to leave and return 90 mins before departure? I’d planned to show at 9 am, drop bags and then return the rental car. Are passengers immediately directed to security after check in or are you free to roam a bit?

No, you can roam a bit if you'd like and return the rental car. But, I'd keep an eye on the lines in security and wouldn't cut it too tight. You should be fine.

Thanks.

Just make sure they are open early. Delta and Spirit didn't open until noon when we flew back at the end of January

They are open early for a 12:15 flight

Actually the counter didn’t open till 10am. Got there at 9am and after 20 mins my wife and daughter held the place in line while I booked it to the car rental company to return the car. Got back at 9:50.