I did something similar at the Zürich airport and gained access to a second four hour window of free wifi. You had to bind your MAC to your identity either via SMS or via boarding pass, two independent channels. Only problem was that I only had an android phone without root. So I disabled MAC randomization for that wifi, deleted the cookie, and signed up via boarding pass. Never felt more like a hacker (and I hacked dozens of active directory domains to domain admin on my job).