Though it's been greeted with rapture by some travel websites, I'm not entirely enthused about JetBlue's recently-announced All-You-Can-Jet Pass for $599. That device gives you the right to make unlimited flights on JetBlue, for one month between September 8 and October 8, for all of $599. And quite clearly, if there were a reason for you to make daily flights on JetBlue for 30 consecutive days, you'd save big by first buying the Pass. But that would involve an abnormal amount of flying.

If you're simply eager to make weekly round-trips aboard JetBlue (which is surely more realistic), the mathematics don't always work in your favor. That's because a great many JetBlue flights are considerably below $100 in price -- like its one-way fare of $64 between New York and Portland, Maine, or to Boston. Takes a lot of those short flights to total $599.

Moreover, it's a requirement of the Pass that you buy your tickets at least three days prior to each flight -- you can't simply and frequently board those flights without a great deal of advance planning. So consider the following extra example:

In one month, let's say, you decide to fly round-trip between Long Beach, California and New York City, to visit relatives for a full week in either city. There are one-way JetBlue fares as low as $119 in one direction, and $139 in the other direction, a total of $258 for a week in either California or New York. Then you fly round-trip between New York and Montego Bay, Jamaica, for a dandy beach vacation of a week. That costs $174 each way, or $348 round-trip. Add both round-trip flights -- a trans-continental trip for a week and a Caribbean trip for a week, a great deal of vacationing to squeeze into a single month -- and you've spent a total of $606. You've saved a total of $7 by committing yourself to the purchase of an All-You-Can-Jet Pass.

Now obviously, if you make such a trip each week, and thus stay continuously away from home for a solid month, or nearly a month, you can save by purchasing the Pass. But how many of us do that? How many of us make a minimum of four long-distance trips a month?

I may have missed some special needs that one or more of our readers may have. Maybe there's somebody who wants to fly round-trip to Florida on eight different occasions in one single month. Or maybe even only four round-trips to Florida in one month, each costing about $200, would make the purchase of a Jet-All-You-Can Pass useful.

But I don't think so.