For many CEOs and their families, it's an annual question: Go skiing in the Rockies for spring break, or bask in the sun someplace south?

Then again, some do both. That was the case this year with the CEO of a commercial real estate firm in New York. Along with his wife, their four children and a nanny, he flew first to Vail, where the family skied for a week. Then they took off for Mexico and a week of snorkeling in Cabo San Lucas.

Each time, they flew on a private jet--an eight-seat Citation X provided, along with a pilot, by Marquis Jet Partners, one of several companies now selling memberships for private-jet travel. 'Without his Marquis plan--25 flight hours a year for about $200,000--the CEO says his family never could have pulled off their lavish two-week trip.

"There's no way to get from Vail to Cabo other than maybe take a plane to Los Angeles and wait around at the airport. This way, boom--you get on, you're off," he says, noting the trip took two hours by private jet and the scenery seemed to change at once from snowy peaks to the turquoise waters of the Sea of Cortez.

As any CEO who has hopped on a corporate plane knows, traveling by private jet is a world apart from taking even a first class commercial flight. There are no snaking lines at the airport, no tedious layovers and no threats of lost luggage, to say nothing about security and reliability.

But despite its appeal, many chief executives have limited their use of private aviation to business trips. In an age of scandal, CEOs may be reluctant to use company planes for personal tips. Buying a jet, or even a fractional share of one, can run well into the millions and require a multiyear commitment. Chartering a flight with a service whose aircraft and pilots are unfamiliar to you can raise safety concerns.

Seizing on this untapped market, companies such as Sentient, Delta AirElite and Marquis are offering private-jet memberships. For a minimum of about $100,000, you can buy prepaid blocks of time on jets that seat from six to 14 people.

The response has been strong. Sentient, the Boston-area company that pioneered the concept four years ago, has more than 1,200 members. Its single-year sales increased 78 percent last year, says CEO Mark Stone. Marquis says it sold 500 memberships in 2002, its first year in business. This year, the New York-based company expects to at least double that.