Private jet cards are similar to debit cards in that you prepay a set amount of money into an account and then money is withdrawn from that account each time you use it. The two big differences are the amount of money, for jet cards, it’s usually between $100,000 and $500,000 and that you don’t really swipe, you or your assistant calls your customer service rep or in some cases, you can make your request via an online app.

By any stretch of the imagination, even for a billionaire, $500,000 is not chump change, and many purchasers already own planes but need a supplemental lift. Think of the Ultra High Net Worth (UHNW) family like your family. You often need more than one car at one time, so Super Rich families need access to multiple planes sometimes, but not often enough that it makes sense to own a second plane. This goes for companies with one or two planes also. Or sometimes, you might need a larger and longer range plane. Either way, jet card and prepaid block charter program customers typically fly privately between 25 and 500 hours a year.

According to Business Jet Traveler, in selecting the right program, 76% choose the program based on the recommendation of a friend or experience with the provider often is hitching a ride with a friend followed by 9% who simply searched on the Internet. Only 5% used a broker and only 3% used a consultant, the latter being a very small number for such a big purchase with lots of variables.

In trying to write a story for Forbes.com about buying private jet cards and prepaid private jet programs, I put found over 75 different programs with 62 points of difference from hourly rates, standards for sourcing crew and airplanes, policies on flying unaccompanied minors, minimum daily charges and so forth.  To assist buyers I’ve put them into a series of easy-to-use spreadsheets and broken them into logical chapters.

You can find it at PrivateJetCardComparisons.com.

Some more reading about private aviation: