If they are filtering on MAC, you could pick up a USB WiFi adapter which will have its own MAC. Once the drivers are installed you can just disable the internal NIC and connect using the USB NIC for another 45 minutes. That is a bit easier than spoofing the MAC. As an added benefit, some of the USB Wifi adapters have higher tx power and better range than the onboard adapters, and at least domestically, the USB connection isn't likely to be any slower than the bandwith the airport provides.