We've traveled a lot with scooters. We used to take the bars off and either carry the two pieces in a backpack on to the plane. That works, but as bars get taller and wider, it's a pain. We've also taken the bars off and packed the scooters in our large luggage bags that we check. there's a risk in that, however, as there's always a chance that the bags could get lost or delayed. You don't want to risk that on the way to a scooter destination.
A friend of ours showed us a new method recently that works really well. Leave your scooter completely intact and take it with you, through security, to the gate. When you go to get on the plane, check it with the gate staff. They will put a tag on it and check it for you. When you get off the plane, the scooter will be waiting for you at the next gate. While that has worked a few times, you might want to consider verifying with the airline that this method will work.