I have taken a Triplett Zephyr many times on airplanes. I worried a lot at first, as the dimensions didn’t quite match what they were requiring, but I have never had a problem. I did have problems with a Stoney End Eve, however, twice. I was forced to gate check it with the baggage. I was a wreck the whole flight, both times. The Eve is slightly larger than the Triplett. I don’t know how they compare to the harpsicle… I am guessing the harpsicle is larger than the Zephyr, but don’t know for sure. Hope this helps!

I’ve taken a harpsicle on a plane several times, some years ago. The planes were 737s. I was able to put it in the overhead and also in the closet intended for coats for first class passengers. I think airline employees are sometimes inconsistent in applying rules – some attendants didn’t seem to care that I put it in the closet, others were not happy with me. So you take your chances. I never had to check it, thank goodness, but it certainly added stress to the trip until I had the harpsicle stowed and me in my seat!