The Wall Street Journal (subscription required) revisits the issue of fare errors, most recently discussed here a few weeks ago.

While the article asks the important question — when are such fares honored, and when are they canceled? — it still offers no conclusive answers. As I’ve argued before: in the world of travel, you sometimes just don’t know, simply by looking at the price, if a rate is an error or a promotion.

The airlines (American and Delta are singled out) reportedly are trying to build escape clauses into their contracts of carriage and fare rules, in case of an “unreasonable” fare, but even then, what really is an unreasonable fare when Ryanair sells tickets for just the tax?

Once a purchase is confirmed, with ticket numbers, confirmation numbers, and a charge to your credit card, you should be pretty safe. My advice: Book first, always pay with a credit card (for the purchase protection benefits), and wait to ask questions later.