Yes, you can switch devices and continue to use the FlyConnect service. On long-haul routes (with A330neo aircraft), you'll receive login details after purchase, which you can also use to log in on other devices. You'll then be automatically logged out on the original device.
You can also switch device on short and medium-haul flights (with A320neo or A321neo aircraft). To do this, you need to click on "Transfer WiFi" in the FlyConnect portal using your other device and then enter the email address you used when purchasing the internet package. As soon as the system has found your purchased internet package, you can activate it on the new device. You'll then be automatically logged out on the original device