I am unable to purchace an in app purchace for foreflight pro 1 yr subscription

If you would like help from these user-to-user forums then you will need to provide more information than 'unable to purchase' - what happens when you try to buy it, does the 'buy' button not work, if you are getting an error message then what does it say ?

If you are getting a message to contact iTunes Support then you can do so via this link and ask them why the message is appearing (we won't know why) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption

If it's a different problem ... ?