I think you still can. It is the area from the Land Wafare hall to the end of the airfield that is now blocked off. However, some years ago they changed the parking arrangements which mean that only the disabled and a few others can park up the east end of the airfield. This means that on a busy airshow day, if you are at the western end near where you have been before, it is packed like sardines.
It will be much better irrespective of where you park to walk up to the eastern end where there is likely to be much more space and if you take photographs of flying aircraft , better for that too as they are likely to be closer at the end of the crowd line when they come round the corner and in better light.