Originally Posted by mre5765

It was part of the ticket price because the marginal cost of checked luggage was small enough that it wasn't worth risking pax ill will to charge for it.

Now with fuel prices higher (albeit, in utter free fall), the marginal cost is now high enough to charge for it.

I think in addition to the stick, UA ought to add a carrot ... RDMs for pax who don't check (including gate check) bags.

And given how few paid F pax there are in domestic cabins, paid F pax do not subsidize upgrades; they subsidize people paying discount coach, and until recently, they were subsidizing the bulk of checked baggage cost from backpackers and Kettles.