With the Northwest/Delta merger now underway, it was only a matter of time before they started the process of combining frequent flyer miles. Right now, they are offering 500 bonus miles to all customers who link their Skymiles and Worldperks accounts by March 15, 2009. If you don’t have one or the other, open it up for the miles!

Once your accounts are linked, you can transfer freely between the programs as often as you like until they are ultimately combined into Delta’s Skymiles program. This creates some very unusual opportunities for flyers. If you have enough miles for a ticket or upgrade award you can search both programs for availability and transfer the miles into your best option for redemption. If you’ve been sitting on miles because you had trouble redeeming them in one program, try the other. I’ve always loved Worldperks and found it much easier to cash in miles there than anywhere else.

The promotion also gives American Express cardholders a chance to cash in Membership Rewards for Worldperks by depositing them into their Skymiles account and transferring them over.

There are a few things to be aware of. Transferred miles will not count as Elite Qualifying miles on either airline. Also, Northwest will count the transfer as activity to extend the expiration date on your Worldperks, but Delta will not for Skymiles. That means if your Delta miles are about to expire, the transferred Worldperks would expire on the same date so be careful and make sure you don’t lose everything!

All in all, I think this is a great feature. Although it is only temporary, it will make the merger much smoother and keep frequent flyers on both sides happy…at least for now!

You can link your Delta and Northwest mile accounts and read the full list of terms and conditions here.