Just got this update:
We have some important information about your United Wi-FiSM subscription purchase on April 10, 2017.
Due to a technical issue, we offered United Wi-Fi subscriptions before we were fully ready to make them available. We have since removed the option to purchase United Wi-Fi subscriptions.
The good news is that you can still use your subscription until December 31, 2017, and you’ll receive a full refund for your purchase. United Wi-Fi subscriptions will also be available for purchase again soon.
We hope you enjoy your subscription, and we’re sorry for any confusion that this may have caused.
United Airlines Wi-Fi Team