I love the airline stock sector. Just when you think it’s safe to stay in the water….

<Insert the theme from “Jaws” here>

Last week the sector enjoyed one of the best week’s it has had in, well, weeks, with the majority of the stocks we track here at PlaneBusiness posting nice double-digit gains.

Today? Not so much.

And tomorrow? Probably worse. Much worse.

After the close of trading late this afternoon Continental Airlines announced its traffic numbers for November, along with its RASM estimates.

The numbers were not good. Ugly might be a better way to describe them.

You can read the release here, but here’s the Cliff’s Notes version.

Consolidated load factor was down 2.8 points to 77.3%, while mainline posted a load factor down 2.6 points to 77.8%.

On a consolidated basis, traffic was down 10.5% while capacity declined only 7.3%.

But here’s the nasty news. Consolidated passenger revenue per available seat mile is estimated to have increased only between 1% and 2% compared to November 2007. while mainline passenger RASM was up between 2% and 3%.

To put these numbers in perspective, last month the airline posted a consolidated RASM figure that was up 9.5% over October 2007, while mainline passenger RASM was up 10.4% year-over-year.

In addition, these estimates are also below recent analysts’ estimates, and the airline’s own recently revised guidance, which had the airline posting RASM increases of between 4% and 6%.

For those of you who don’t follow the sector that closely, the RASM numbers that Continental reports are looked upon as an indicator for the rest of the industry. Sometimes the airline can be a bit above or below the rest of the pack for various reasons, but most of us airline financial types still use their “first out of the box” look at RASM as a kind of indicator as to what’s on the horizon.

If this is what Continental did for the month, I’m not sure I want to see any more numbers.