At Keflavik Airport, only four main car hire companies have their offices inside the Airport building; for the other ones, there is a shuttle bus service operating. Since I'll be arriving quite early at the airport to drop my car off (around 5 am), I was wondering if there is already a shuttle bus service this early, and if yes, when/how often it runs. Unfortunately, there is absolutely no information about this service on either the homepage of Keflavik Airport, nor on the sites of some the car hire companies which are out of the airport (like Alamo).
Does anyone know anything about this service?