I think my 31" plastic Samsonite is slightly oversized, but no airline has noticed or cared so far in 15 years. They look at weight and anything oddly shaped, but ignore the ones that look like conventional big suitcases.
If the Helix fit in one of these, I would have no hesitation about taking it on a flight. I'm hoping it would just be taking out the seat post and pedals and deflating the tires.