my point is that if you are going to an airport to catch a plane, the chances are you will be going for a reason, most people who go to airports aren't ridiculously well off people who can afford to go on holiday whenever they like, whereas most other businesses are different from this. you may have got up ridiculously early to catch said plane, you will mostly likely be tired, stressed, nervous anyway and you won't take kindly to a bunch of people barricading the airport.
i'm all for direct action when it works, but i can only see this annoying and inconveniencing the public, and allowing big business to paint the protesters in a similar light. other tactics need to be used. occupying offices - very effective. if you end up missing your flight because of these people you are hardly likely to be sympathetic to their cause or support future actions that they take, whereas if this happens DIRECTLY TARGETTING THE PEOPLE YOU ARE AIMING TO TARGET (ie not the customers,not the workers, but the bosses of these companies) - ie barricading/occupying offices, and the like, you are more likely to gain popular support than if thousands of people miss their holidays or potentially very important trips because of your publicity seeking actions