IF WE'RE KICKING around who has the worst job in the world, my vote goes to anyone in customer relations for Southwest Airlines.

I say this because the airline is catching major heat for announcing that, starting Wednesday, it'll begin charging obese passengers for two seats on its daily flights.

Personally, I can think of a lot of people who should be charged double when they fly.

People with babies who wail nonstop -- I wouldn't mind seeing their VISA cards banged twice.

Or people who fall asleep on your shoulder and leave a thin river of drool as a tasteful memento.

But at least for now, the only fliers on Southwest being charged double are "persons of size" who can't fit into the standard airline seat. (The standard seat, by the way, is somewhere around 17- to 18 3/4 -inches wide, which means anyone bigger than Snap, Crackle and Pop probably feels cramped.)

Southwest says it has had this policy for more than 20 years, but that it was only enforced on fully booked flights. Now, though, obese passengers will have to buy two tickets regardless of whether the flight is full.

As you can imagine, this is not going over very well with the various organizations that advocate for the obese, even though other airlines have similar policies.

When I called the National Association for the Advancement of Fat Acceptance -- yes, there really is such a thing, it's based in Sacramento, Calif., and has 4,500 members -- spokeswoman Maryanne Bodolay said Southwest's policy "is like sanctioning open hostility against fat people. There's already enough air-rage."

Oh, she's right about the air-rage. Although I'm not sure how much of it is directed at the very overweight.

Personally, when I fly these days, I'm more concerned about some member of the Future Martyrs Club stepping into the aisle with six sticks of dynamite strapped to his chest than I am about the fat guy in seat 3C.

And I get way more ticked off about my flight getting canceled with no explanation than about the gal in the next seat who's obviously been hitting the Breyer's Dutch chocolate too hard.

Bodolay said her association has two main concerns with Southwest's policy: "How do you implement this? And how do you do it with sensitivity? Who gave them this policy -- Howard Stern?"

In addition to getting off a great line, Bodolay makes a great point. She wonders, for instance, whether a skycap, ticket agent, gate attendant or flight attendant would be the ultimate arbiter of "who's too fat."

"It's relying on the graciousness of employees," she said. "Are we going to get a flight attendant who's biased toward fat people?"

When I called Southwest, spokeswoman Christine Turneabe-Connelly said the airline hopes its customers "monitor themselves" as to whether they're too large to fit in a single seat.

But if that doesn't happen -- and this being the real world, I don't foresee any ultra-large passengers sidling up to a ticket agent with their MasterCards and saying "Aw, hell, you gotta charge me double" -- she said customer service agents at the ticket counter and at the gate would be responsible for determining who would have to buy two tickets.

"I can't stress how discreetly they will address this issue," she said.

Well, I certainly hope so. That's all we need, a big scene in front of the Southwest counters, roving airline employees with bullhorns barking "You, with the size Triple X Nike T-shirt and sweats, come with me, please."

You think airports are tense now?

With the Fat Gestapo circulating, it'll be unbearable.

Bodolay said her organization would prefer that Southwest "compromise" and "open a dialogue" to see what else can be done to help larger passengers.

Among her suggestions: Airlines might consider installing a special row of larger seats on each plane, a row that goes only two across.

And if the airlines insist on charging larger passengers more to fly, charge them for half an extra seat, not another full fare.

"When I fly, I don't take up two seats," Bodolay said. "I take up one seat and about a quarter of another one."

Bodolay said her association has heard from hundreds of its members who vow never to fly Southwest again.

"The PR on this might shoot [Southwest] in the foot," she says.

But Turneabe-Connelly said the "vast number" of complaints received by Southwest are from "customers who have had their seat encroached on" by larger passengers.

Anyway, the fun begins Wednesday at Southwest counters everywhere.

Why do I get the feeling you might see a few lawyers there, too?