Can I upgrade from a Standard subscription to Professional?

Yes. Please log in to the site. Click on My FlightStats in the upper-right corner of the screen and then choose My Account. This will take you to your Account Preferences. Click on the Payment Information tab at the top of the screen. This screen will show you your current account status. If you already have a Standard subscription, there will be an Upgrade button next to your account status. Press Upgrade, and confirm that you want to upgrade.

Your credit card will be charged for the upgrade and your first month's payment will be different from remaining months. The USD $2.99 you have already paid for standard subscription will be deducted from the USD $24.99 monthly rate. The amount charged will be USD $22.00 pro-rated based on the amount of days you have left on your normal billing cycle. The full USD $24.99 will be charged on the next month's billing cycle.