Originally Posted by
MSPeconomist
I also find the rule very strange in that the total weight loaded onto the aircraft is the same regardless of whether someone carries or checks the bag. I guess the balance part could matter if it's preferable to have weight in the cabin rather than in the belly of the aircraft. However, I'm inclined that the real issue if space (volume) for cargo rather than weight per see.
Strange is in but true it also is. I flew the CRJs for years and we would often bring carryons that had been planned to be put in the cargo hold back up into the airplane where they magically no longer counted in Weight and Balance. Carryons in the cabin are included in passenger weights. Carryons loaded in the cargo hold weigh 30 lbs each. That's the magic of the FAA for you.