Normally, if you’re traveling with a dog you plan to carry on you either have to make your entire reservation over the phone to ensure that there’s space on your plane(s) for an in-cabin pet, or make your reservation on-line and call back to add your dog to your reservation. The first option is expensive (a lot of airlines now charge a fee for phone reservations) and the second option is a bit risky, because you don’t know if there’s actually room in the cabin for your dog when you commit to your reservation.

Northwest Airlines has not solved the problem, since you still need to make your reservation first before going back in and adding your in-cabin pet. However, they now allow you to add a pet to your reservation on-line, instead of calling customer service. It’s a small, but nice, step forward — at least you don’t have to grapple with the airline’s phone system and wait for a customer service representative to become available.

Here’s what you do: After you’ve made your NWA reservation, go back to the website and log in. Find the “Reservations” tab and click on the “Manage My Reservations” option, which will take you to a “Travel Reservations Summary” page. Click on the “Details” button next to the trip you want to add your dog to. On the page that shows up next, you’ll see an “Update Reservation/Add Information” option. From that menu, choose “Add carry-on pets,” then click the GO button. NWA’s pet policy comes up, and at the bottom of the page there’s a place to enter the number of pets you want to bring with you in the cabin. Continue to the next page, where you will enter details about the type of pet you’re bringing (dog or cat) and about your carrier, and make payment by credit card.

I suggest printing out the receipt they offer you and adding it to your travel documents, so that you have proof in hand that your pet’s reservation has been made and paid for.

4/12/10: Alas, this post is now moot, since Northwest has been acquired by Delta, and Delta does not allow you to book your pet on-line when you make your own reservation. Instead, you need to make your reservation, then call to add your pet to your reservation.