On my last trip to take my cruise, I flew out of Philadelphia Int'l Airport. I requested an electric cart to take us to our terminal since I was traveling with my 85 year old mother and my two teens that have congenital myasthenia. Basically they have a muscle weakness and get easily fatigued. Technically, they have a somewhat invisable disability. When the cart arrived & we proceeded to get on it, I was told that since there was nothing wrong with my teens, they had to walk. I tried to explain that they have a disability but the driver kept arguing with me, to the point of me asking to see a supervisor. Again, she agreed with the driver of the cart and finally instead of making the scene even worse, she finally agreed to let us all on. I just want to say, that just because you can't see a disability and the person is young, people should not assume that they don't have any. People have been very rude to us and assume it's the older people with disabilities, not young ones.