can you return a car if you are not open. You guys dont open untill 5:45am and my flight leaves at 6:00am

I didn't think you could do that. I would check.

I drop my rental car off early all the time. Obviously, just make sure you have all your stuff out of your car before you drop the keys off!

Normally there is a key drop box near the rental car return kiosk. Just verify where the drop box is when picking up your car. Lot of folks need to drop off befor rental cars locations open.