Back in June Blackberry sponsored a promotion offering free inflight internet access to their customers on Gogo-equipped flights. It was a really useful promotion, since they verified you were a Blackberry user based on your browser's "user agent," which is easily spoofed.
Well, Gogo is back at it again, this time with a promotion sponsored by Allstate. They're offering 30 minutes of free in-flight internet on weekend flights on users' "mobile devices," i.e. smartphones. I have to assume this promotion applies on a per-flight basis, so you should be able to get 30 minutes of wifi per flight, not per weekend.
If you are actually using the internet on your mobile phone, then enjoy! There's no need to hack this promotion.
However, I believe that they're almost certainly verifying your device type this time the same way they did during the last promotion: based on your browser's "user agent." That means if you want to enjoy 30 minutes of free wifi on your laptop, instead of or in addition to your smartphone, you should be able to use the same technique as last time to "spoof" a smartphone browser and get your 30 minutes of access.
I'm taking my next Gogo-equipped flight on October 11, and I'll post an update when I land verifying that this hack works.