I have found the SeaTac rental car return to be aggravating. The buses come at unpredictable intervals — even at 530 am when there is little traffic. As it is a completely separate building there is no walking to the terminal. People have varying amounts of luggage so it can take time to load the bus.

i like to get the receipt and make sure the agent signs off on no damage; sometimes there can be a wait for that.

I would estimate at least 40 minutes to return car and get to terminal but it has taken longer at SeaTac — 60 to 70.