Your next cruise could earn you thousands of miles

You don't have to give up earning miles when you choose to travel by sea rather than by air. Five airlines—Alaska, American, Continental, Frontier, and United—have their own cruise booking sites, where you can earn up to 10,000 miles per cruise, in addition to miles earned for the flight to your departure port. Plus, Northwest, United, and US Airways allow you to earn miles with their cruise partners.

Airline cruise sites

When it comes to airline cruise sites, there's United Cruise4Miles and then there's everyone else. That's because Alaska's Mileage Plan Cruises, American's AAdvantage Cruise, Continental's OnePass Cruises, and Frontier Airlines Cruises are all operated by National Leisure Group (NLG), and therefore offer the same pricing and specials. (America West also has a cruise site run by NLG, but the airline does not offer miles for cruise purchases.) In contrast, United runs its own site and contracts directly with 17 cruise lines.

The four NLG-branded sites only feature cruises offered by the World's Leading Cruise Lines: Carnival, Costa, Cunard, Holland America, Princess, Seabourn, and Windstar. You will earn 10,000 miles for a cruise of 13 or more days, 5,000 miles for a cruise of nine to 12 days, 3,000 miles for a cruise of six to eight days, or 1,500 miles for a cruise of one to five days. Miles are awarded per stateroom to only one passenger per cruise.

United Cruise4Miles offers one mile per dollar spent on the price of the cruise plus taxes and fees, and is the only site that lets you redeem miles for a cruise. A three-day cruise costs approximately 30,000 to 35,000 miles, and a seven-day cruise costs approximately 65,000 miles, depending on destination, departure date, and cruise line. One benefit to purchasing your cruise through United is that miles can be deposited into more than one Mileage Plus account, so several guests in one stateroom can earn miles.

If you're looking to get the most mileage out of your cruise, you are better off booking with one of the NLG-affiliated sites, rather than with United, because you'll earn more miles. A seven-day cruise booked through Alaska, American, Continental, or Frontier will earn you 3,000 miles per stateroom, no matter the cost of the cruise. However, as United cruises earn one mile per dollar spent on the cruise purchase, a seven-day cruise for two people will only bring in 698 to 1,198 miles (based on average cruise prices of $349 to $599 per person).

No matter which airline you choose, remember to provide your frequent flyer number when you book your cruise in order to earn miles.

Airline sites versus cruise agents

It's tempting to rush out and book your cruise with an airline site and earn thousands of valuable miles. But will you get as good a deal as you would through a cruise line website? A spokesperson for United told us that Cruise4Miles receives top-tier recognition from the cruise lines due to its high volume of sales and can therefore negotiate competitive rates. And, according to its website, the National Leisure Group is "North America's largest provider of cruise vacations."

However, we decided to put the sites to the test. We compared the prices found on the special offers pages of United Cruise4Miles and the four NLG sites with the specials found on Carnival, Norwegian, and Cunard's websites. In all cases, we found prices that were the same or cheaper than the cruise companies' own deals. It is always best to shop around because prices will vary according to the specific cruise and how far in advance you're booking, but our test proves that you can get competitive rates and extra miles when you book your cruise through an airline's site.