I have brought my helmet onto the plane, I did not want to pack it where it might get damaged. And I have brought things like pedals on a plane.

Surly rack would probably fill up the carry-on size checking bin if you are lucky. Do you have a fabric bag about the size of a carry-on that you could put the rack into, then put the other stuff that you were going to put into a carry-on into that bag?

Most airlines do not have a weight specification for carry-on, in that regard you are lucky.

I have no clue if a TSA inspector would think the rack is a weapon. If so, you lose the rack.

***

I mentioned above that I used to have a Surly rack. When I switched to Tubus low rider racks, I bought the little Nashbar rack that bolts onto the fork cantilever brake mounts. But more and more newer bikes lack the cantilever mounts. This way I get the low rider rack and the platform rack. And for riding around home, I take the low rider rack off but keep the platform rack.

In the attached photo I have the Tubus Ergo and the Nashbar rack on one of my bikes. (The wiring looks sloppy because the tour lasted two weeks, the light was only installed for a two week period so I did not try to make the wiring look pretty.)