Q: If I buy an iPad Air on sale from Best Buy, can I purchase AppleCare for it through Apple.com?

Important notes

Purchase AppleCare+ with your new iPad. Or buy it within 30 days of your iPad purchase:

• At an Apple Retail Store (inspection of iPad and proof of purchase are required)
• OR call (800) 275-2273 (requires you to run a remote diagnostic and provide proof of purchase)

See AppleCare+ Terms and Conditions for complete product details.

You must meet those requirements. But you should be able to purchase the warranty. I copied the information from here.

http://www.apple.com/support/products/ipad.html

Just so you know, the BestBuy sale ended already.

Yes, you can. THat's that I did. But I would also suggest that you look into Best Buy's own warranty. I believe they offer  a couple years of accidental damage protection for less than the Apple out of warranty replacement cost.

What's covered may vary but could be something to look into.