You do this by entering your billing information, then selecting a different plan for the "Application" you want to update.
First, enter your billing information. To do this, sign in to https://developer.flightstats.com, click "Account" in the upper right of the page, then "Credit Card Details" in the right-hand navigation.
Next, navigate to the application. In most cases, as an Evaluation user, you will have only one application; this is what associates your API authentication credentials with a billing plan. To do this, select "Dashboard" at the top of any https://developer.flightstats.com page, find the application in the list on that page (unless you edited it, it will be called "Default"), and click the "View" button. At the bottom of the page you'll see a line showing which plan is associated with this application, followed by a link to change it. For example:
Plan: Evaluation Plan (Review/Change)
Click the Review/Change link. This will show the available self-serve plans. Click the one you want, then click the "Change Plan" button. You should see a confirmation message "Plan change was successful" at the top of the screen, and you will receive an email confirming the change. There is a final step if your access was suspended due to exceeding the 30 day Evaluation Plan limit. In this case, please contact our specialists or open a help desk ticket to request that your account be un-suspended.
If you have any questions about the plans offered, review the Pricing page for more details (log in required):
Converting from the Evaluation Plan to the Commercial Plan will immediately disable your free trial access to any Premium APIs. To avoid possible disruption, we encourage you to contact us early to allow sufficient time to review Contract Plan terms and pricing with our specialists.