That's also how I read it, which astounds me. Would be technically impressive if it worked like that. And extra vindictive since even if they don't allow rooted devices to play DRM'd video, there's no good reason why they should also be prevented from buying in-flight internet.
(one solution if that's really how it works: rotate your mac address, reconnect, and then never open up the United app again so it can't squeal on you.)
This is pretty common, as stupid as it is. Snapchat would do this too for jailbroken phones, only they'd also permanently ban your account. It was an arms race between snapchat and tweak developers masking jailbreak detection methods for years at least, maybe still ongoing.
The odd part is tying the airline's app to a wholly separate thing run by Panasonic (the onboard wifi). The United app isn't required, involved, etc, in purchasing and using wifi on the aircraft. No app is required at all...just the browser on the phone. That's why we're confused about the integration that would be needed to accomplish this. The United app would have to be detecting the jailbreak and then sending some unique identifier to the third party via some separate channel.
You could also wreak some havoc by banning the macs of other devices on the plane that want to use the WiFi...so I'm pretty skeptical this cross-service integration is really there.
(one solution if that's really how it works: rotate your mac address, reconnect, and then never open up the United app again so it can't squeal on you.)