From here
Much as I agree to the above comments that AENA airports are usually a pain in the neck, there is some progress..
According to this, there is now a possibility to pay landing fees on-line. Call the ARO when you land and they will mail you the bill and you can pay via an app. How long does it take to receive the bill? Well, hopefully shorter than the waiting time for the fuel truck 
https://realaeroclubdeespaña.org/nuevo-tpv-virtual-de-aena-para-pagar-tasas-sin-bajar-del-avion/
