It really depends on the airline and how long the flight is. Some do, some don't. It'll be more likely to be found on longer flights, like international ones.
OP: I can't find the details on your specific model, but the stock battery that it comes with is a 6 cell. the 12 cell battery will give you VERY close to double what the 6 cell you have now gaves (at least a NEW 12 cell will give double what the 6 cell gave when it was NEW). So if you get 3.5 hours with the factory battery, expect about 7 (or just slightly less) out of the 12 cell. Pesonally, I never been able to actually work more than about 3-4 hours on a flight anyways (even on the 14 hour stgo-madrid flight).