My companies guidelines....
Alcoholic beverages in retail packaging may be carried as checked baggage.
For alcoholic beverages less than 24 percent alcohol by volume (including most wines and beers) there are no restrictions on the amount that may be accepted in checked baggage or purchased after completing security screening at the checkpoint (Duty Free). If traveling internationally, alcoholic beverages may subject to customs limitations in the arrival country and transporting alcoholic beverages may subject to country regulations.
For alcoholic beverages between 24 and 70 percent alcohol by volume there is a limit of 5 liters (1.3 gallons) per customer that may be accepted in checked baggage, or that may be purchased after completing security screening at the checkpoint (Duty Free). Packaging must be in receptacles smaller than 5 liters. Alcoholic beverages more than 70 percent alcohol by volume will not be accepted.
All alcoholic beverages must be packed to prevent breakage. Continental shall not be liable for breakage or spillage of alcoholic beverages. Normal checked baggage allowance limits, excess fees and carry-on limits apply.
Up to 3.4 oz. (100 ml) of an alcoholic beverage may be taken through the security checkpoint is provided it is less than 70 percent alcohol by volume, in a container that is 3.4 oz. or smaller, and in is carried in a plastic zip-top bag.
If you are flying to the U.S. and have a connecting flight, even duty free liquids that meet U.S. requirements will not be permitted through U.S. security checkpoints. If you have a connecting flight, liquid duty free purchases must be placed in your checked baggage. Since you will be required to reclaim your checked bags prior to passing through customs inspection, you can place duty free liquids into your bags and recheck it for your connection.
Note: Alcohol transported on an airplane cannot be consumed on board
My real concern would be how would the pressure affect the keg?