Let’s fast-forward to Aug. 1, when US Airways begins to charge for soft drinks on its flights, including bottled water. How’s that going to go over?

Not very well. In fact, over the long term, depriving passengers of basic necessities like drinkable water could cost the carrier more than the revenue it will generate.

Let’s clear up a few things first.

The “free” water on the plane is city tapwater that’s been sitting in the tank for hours. It’s gross.

We can’t bring bottled water through a TSA screening area under the agency’s ineffective and widely misunderstood 3-1-1 rule. So you basically have to buy the airline’s water at $2 a bottle, which is a steep markup from the grocery store price.

If you’re a budget traveler, you could find yourself strapped in an economy class seat on a long flight with nothing to drink and no money to pay for essential water. And that, say passengers like James Hammett, can be extremely dangerous.

He ought to know. On a recent international flight, his sister became dehydrated and had to be treated by a doctor.

In the era of free drinks, she had not drunk enough to avoid this problem. If people start having to pay for water, their natural inclination is going to be to reduce their consumption. How long until the airlines start getting claims for reimbursement for doctor or hospital visits — or lawsuits?

I have no problem with charging passengers for sodas and fruit juices, nor do I think most passengers would mind paying for those items. But drinkable water? That ought to remain free.

Common sense tells you that. Alas, common sense appears to be in short supply.