This is a question that I asked a couple of years back. Everyone told me not to worry,that it wouldnt happen. And they were right. I have only flown once but I had no problem at all and I don't think I have met or read about
anyone that has had the problem either. I know of one young man that makes many plane journeys due to his job and he says that he hasnt had a problem with the bag balooning at all.