A promise of free airfare is certainly enticing, particularly with today’s sky-high prices. But if you respond to unsolicited letters that congratulate you for qualifying for two round-trip tickets, prepare yourself for some turbulence.

The tickets may be bait to lure you to a high-pressure sales presentation by a “vacation club” whose promises of huge travel discounts and top-tier accommodations may never be kept, despite memberships that cost upward of $9,000 upfront with hard-to-cancel annual fees.

Scam Alert first exposed these clubs in 2007, but they have recently been up to their tricks again, according to the Better Business Bureau.

In Connecticut, the bureau has issued new warnings about “award letters” arriving in that state from Nicholson Barnes, a sweepstakes marketing company that the bureau has given an “F” rating. Although the letters don’t mention it, you can’t get your freebie airfare unless you attend a sales presentation by Triton Travel Group, a franchise of Outrigger Vacation Club.

Outrigger is one of three companies recently sued by Massachusetts Attorney General Martha Coakley for allegedly selling vacation club memberships that don’t deliver on promised travel discounts.

The other two companies—Massachusetts-based Only Way 2 Go Travel of Plymouth and Fantasia Travel Group of Methuen—are accused of conspiring to sell Outrigger Vacation Club memberships in a bait-and-switch scheme. Charles Caliri, president of both companies, said in a telephone interview that his companies “are not scams. In the near future, you’ll see that a lot of these accusations will be dropped.”

An Outrigger representative who would not identify herself declined to comment on the lawsuit, and responded to questions from Scam Alert by saying her company “is a third-party service provider.” No response was received to an e-mail sent to Nicholson Barnes seeking comment.

“Consumers will be disappointed if they believe they can simply claim their prizes and walk away,” Howard Schwartz of the Connecticut BBB tells Scam Alert. “They may be pressured into making a snap decision to commit thousands of dollars for a membership or other product that is not as good a deal as they believed or were led to believe.”

Sure, there are many legitimate players out there, but you should keep alert for the shady ones.

How to protect yourself

• Be wary of promises of free airline tickets or other incentives such as show tickets and dinners for two. You may never collect them.

• Do your homework. A simple Google search of a company name—and at the BBB website—can alert you to problems. Also, contact your state attorney general’s office to learn about past complaints.

• If you do attend a presentation, never sign anything there. Many contracts are riddled with small-print loopholes designed to disadvantage members. You’ll want to carefully review the entire contract—perhaps with a lawyer’s help—away from the hard sell.

• Keep your credit card in your wallet. Some travel club reps demand to see your plastic “for identification purposes” before detailing their offers. But that could be a ruse to put charges on your account. If you’re told you must show a credit card, walk away.

Sid Kirchheimer writes about consumer and health issues.