part of the problem contributing to the rampant sale and trade of AS GGUs and UA RPU/GPU is that anyone can use them. on DL, they have tight control over RUC/GUC because only the named member or their guest on the same flight as named member can use them.

of course, the tremendous benefit of the AS/UA system is that the upgrades can be used as gifts. trading/sale is an unintended consequence. i find tremendous value in GGUs so i hope that they maintain a lot of flexibility and the benefit to the many is not eliminated by the abuse of the few.