Subject a caged laboratory rat to unrelenting stress, and bad things happen. It snarls, bites its tail, trashes its cage.

In other words, it acts a bit like the American airline passenger. Some souls stoically tolerate the maddening maze that domestic air travel has become, but others act out like those rats.

Talk about unrelenting stress. Consider the impact of today's fuel and security surcharges, fees to check your luggage at the curb, and now the decision by at least one carrier to charge for any bag it loads onto the plane.

There's no free food in coach class any more, either. Even the water's a couple of bucks a bottle.

And it's not just about money.

Who can forget the winding ticket and security lines; the gauntlet of screening machines, scowling inspectors and bins for one's shoes and belts and bottles of mouthwash; then more queues and frazzled agents at the gate.

Onboard, packed seats as airlines cut flights to save money; frigid cabin temperatures with no available blankets ? they were eliminated in another cost-cutting measure ? and grouchy service from overworked flight attendants.

But the rats are exacting revenge of sorts, quietly and deviously, since they dare not protest too loudly for fear of interrogation.

According to a Wall Street Journal study, stressed-out passengers are revolting by making a pigsty out of the planes. Into seat crevices and seat-back pockets ? which get only cursory cleaning between legs of an airplane's many flights each day ? they're shoving sheafs of newspapers, the remnants of drinks, even dirty diapers. And they're strewing morsels of food all over the plane.

But whatever satisfaction this brings can be short-lived, since the next container of flying rats ? their connecting flight ? awaits, right down the concourse.