Last year, US commercial air carriers bumped 40,000 passengers, and that's not counting the ones who volunteered to give up their seats. United abruptly changed 3,765 travelers' plans with the involuntary bump, with 62,895 bailing out by choice, NBC Boston reports.

Read the fine print on any ticket and you'll see that when you board a commercial airliner, you are completely at the mercy of the airline's decision about who flies and who doesn't.

The US Department of Transportation can't make airlines change that policy, but it can make them offer stymied passengers compensation packages.

Roughly the rules are as follows: If the airline can get you on another flight to your destination within an hour, they don't have to pay you anything.

If they can't get you on an airplane within an hour of the flight, then they have to pay you 200 percent of your original fare up to $675.

If they can't make the two-hour window, they must offer 400 percent of the fare (up to $1,350).

In an op-ed on CNN's website, aviation lawyer Thatcher A. Stone says that when he and his then 13-year-old daughter were bumped from a flight heading to a Colorado ski vacation in 2004, he lost his hotel deposit and didn't get their checked-in luggage for four days.

He sued and won ($3,100) because the airline had not paid him the right amount and had failed to give him any written statement detailing his rights, as airlines are required to do by law.

An airlines spokesman at the time issued a statement. "We are sorry when this happens, but the Department of Transportation allows overbooking of flights because so many airline customers book flights and then do not show up without previously canceling."

Stone admits that United mishandled the removal of an uncooperative passenger in Chicago on Sunday, but he also reminds all air travelers about the realities of a service so many of us take for granted.

Ever since 9/11, flight crews have been understandably strict about passengers following the rules, Stone says. They need you to cooperate.

"If you become unruly, they can throw you off in an instant. Without recourse," Stone writes. "If you refuse to follow a crew member's instruction, they can throw you off and send you to jail."

Forbes travel writer Laura Begley Bloom has run several stories about people who make a profession out of getting bumped by airlines, scoffing at herself. Until recently.

She was trying to get to Florida from New York with her husband and daughter through last weekend's horrendous weather. After hours of delays, Delta started offering incentives. When the offers got up to $900 Macy's gift cards per ticket, her husband approached the gate to negotiate.

He offered $1,500 per ticket. Delta countered with $1,350 and they headed home with $4,050. When they went to check in for the next day's flight, Delta was already asking for volunteers to give up their seats, again. She turned to her husband and said: "Cha-ching!"

They went to the airport and accepted $1,300 per seat, with grateful passengers and attendants thanking them. Delta even threw in $15 each for lunch, $50 for round-trip taxi fare (they live 10 minutes from the airport) and assurances they would get confirmed seats for the next day. When that didn't happen, they cancelled their trip altogether for a full refund and $1,000 each in compensation.

The family walked away with $11,000 all told and the writer has softened her attitude toward people who exploit bumping for profit.

I was on a flight once across the Atlantic at a time when cigarette smoking had recently been banned on all flights, in all sections (hard to believe now there was a time when smoking was allowed anywhere on board). After the airplane was well out over the ocean, a well-dressed gent sitting nearby, lit up.

A stewardess was on him immediately. Sir, smoking is not allowed. I must insist The man, who spoke with a French accent, brushed her off, pointing to the ashtrays in the arm rests. "What are these for then? Boaf!"

The flight attendant was joined by others, all of whom very insistently tried to make the man put out his smoke. He would have none of it, ignored them and kept puffing away, with a completely self-righteous attitude.

A few minutes later, the captain, a tall, military-looking fellow, appeared in the cabin. He leaned close and spoke in the man's ear very calmly and quietly.

The man visibly stiffened, put out his cigarette and sat erect and polite the rest of the flight. I always wondered what it was the captain said to that guy. Whatever it was, it worked.

Contact the writer at chrisdavis@chinadailyusa.com.