Uh, no. Read the fine print. It is 0.45% on that first $9,999.99 tier that you need to keep on deposit to get the FF credits. It's only the tiered portions ABOVE $10K that earns at least 2.25%. In three months, that's a whopping $11.25 in interest you're earning on your $9,999.99.

https://promotion.suntrust.com/airtran/

You then need to pay taxes/fees on your free ticket, assuming you get the ticket you want with your FF credits against blackouts and other restrictions. I'd prepare yourself for perhaps a $50 out-of-pocket cost.

Yes, you're right about pulling your money out after three months. But if you close your account at SunTrust within six months, I believe that's a $25 fee they're going to charge you for closing your account so soon, so you need to factor that in, as well.

When all is said and done, if you need the flight credits, all your hard work might put you a few dollars ahead by banking your money at SunTrust's insultingly low MMA rates. But not much more than that. Hardly seems worth the effort.