Shares of priceline.com (Nasdaq: PCLN) are fearless.

The popular travel portal shook off an after-hours skid after posting mixed quarterly results on Wednesday, only to pop 9% higher as the day closed.

Fourth-quarter revenue increased 35% to $731.3 million, fueled by a 44% spike in gross travel bookings. Unfortunately, analysts were betting on a 36% top-line spurt.

Priceline fared better on the way down to the bottom line. Adjusted earnings soared 72% to $3.40 a share, well ahead of the $3.09 a share that the pros were targeting. What else is new? Priceline has crushed Wall Street's net income estimates for 19 quarters in a row.

A slight miss on the top? A healthy beat on the bottom?

Priceline's upbeat guidance helped the bulls tug harder than the bears today. The travel website operator's targets of $2.34 a share to $2.44 a share in earnings on 29% to 34% revenue growth stack up well next to Mr. Market's expectations.

Lost in the euphoria, though, there are some rough patches worth watching.

Priceline's revenue growth came in weak because things didn't go so well domestically. A nearly 65% surge in international bookings is covering for a mere 8.5% uptick domestically. This is the first time in years that Priceline has failed to deliver double-digit growth in domestic gross bookings.

Things also aren't looking so hot in the not-so-friendly skies. This is the second quarter in a row that Priceline sold fewer flight seats than it did a year earlier.

Investors should be relieved given how some of the other companies in this space got pummeled this month. Rivals Expedia (Nasdaq: EXPE) and Orbitz Worldwide (NYSE: OWW) sold off after posting disappointing results for the same three-month period. Travel deals publisher Travelzoo (Nasdaq: TZOO) trounced profit expectations but merely met Wall Street's top-line target, and its shares took a 17% beating. At the other end of the planet, it was the same deal with Ctrip.com (Nasdaq: CTRP). China's leading search engine took a hit when it provided weak revenue guidance for the current quarter.

Are you catching the industry's receding hairline here, or I am the only one noticing that it's a little light on the top these days?

Airlines, hotels, and car rental agencies were already skimming more and more in booking commissions. Bookings have been outpacing portal revenue for awhile. However, after watching American Airlines parent AMR (NYSE: AMR) play hardball with Expedia and Orbitz two months ago over, it's clear that travel providers want more control in reaching out directly to travelers.

Priceline remains the speedster among stateside portals, but investors can no longer assume that it's immune to any maladies that may befall its rivals. Shareholders should keep an eye on the booking and revenue trends at all of the publicly traded portals. This receding hairline isn't going to look all that stylish in your portfolio if it continues.

Let's hope the travel portals pack a toupee next time.

What's your favorite online travel play? Share your thoughts in the comment box below.

Priceline.com is a Motley Fool Stock Advisor recommendation. Ctrip.com International is a Motley Fool Hidden Gems selection. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Longtime Fool contributor Rick Munarriz has been leaning on travel portals since the 1990s, but often just books directly. He does not own shares in any of the companies mentioned in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.