You are safe to take your Toniebox on board a plane with you in your hand luggage and to use it in the skies. However, the Toniebox should be turned off for takeoff and landing. You should ideally only turn it on once the plane is at cruising altitude after take-off and take the Tonie off in good time before landing so the Toniebox has 10 minutes to turn off.
Ideally, you should also put the Toniebox in offline mode during your flight, thus turning off the Wi-Fi completely.
If you have any further queries, the best thing to do is consult our support.