Originally Posted by AS Flyer

Totally agree with Eastbay. That said, people aren't usually sneaking in large quantities for consumption on board, they're sneaking in three or four minis and cracking them open on-board. Here's the problem - we have no idea how much one has consumed when they're drinking they're own. Maybe they had a couple drinks at the airport bar before getting on but didn't seem intoxicated at that point. Once on-board they crack open three mini's in the first hour and are drinking, unbeknownst to the crew. Next thing you know, you have a loud, drunk passenger that becomes an annoyance to those around or, in worst case scenarios, someone that is belligerent and combative with the crew or other passengers. Intoxicated people and flying often don't go well together and frequently, the effects of alcohol can be amplified at altitude. When the crew is serving you, they have the ability (and the responsibility) to stop serving you when you show signs of intoxication. They can't do that if they don't even know you're drinking your own little bottles. Hence, the reason you are not allowed to consume alcohol not served by a Flight Attendant. To further that, Alaska, and most U.S. airlines, won't serve a passenger their own alcohol.