While many readers probably wish they had simply put their money under their mattress starting about 7 years ago, and left it there — considering what has happened in the markets the last year — there are those of you out there who are the more adventuresome types.

And some of you may have money invested not just in stocks or bonds or mutual funds, but in ETFs. ETF stands for exchange-traded fund. All-knowing Wikipedia defines them thusly:

An ETF combines the valuation feature of a mutual fund or unit investment trust, which can be purchased or redeemed at the end of each trading day for its net asset value, with the tradability feature of a closed-end fund, which trades throughout the trading day at prices that may be substantially more or less than its net asset value.”

I like to say that it’s similar to a mutual fund that can be traded — just like a stock.

Why am I getting into this Investing 101 discussion today? Because the first airline-only ETF was announced this week.

No nasty comments please. (Like, why in the would would anyone be interested?) Personally, I think the timing is excellent.

Claymore Securitiesis set to launch the first exchange-traded fund focusing on the passenger airline industry — the Claymore/NYSE Arca Airline ETF next month.

The ETF will hold 24 global airline stocks, 70% domestic and 30% international. The top three stocks in each category will be weighted 15% in the case of domestic, and 4.5% in the case of international airlines. That puts the remaining index weights for the 18 other stocks in the ETF at 25% for domestic and 16.5% for international. All holdings must derive at least 50% of their business from passenger airline activity.

For those of you with really inquiring minds, you can read the SEC registration docs here.