a couple of the above posts seem to contradict on the subject of entry to class D airspace. on one hand the letter of the regulations seems to require a flight plan for VFR flights "within class B, C & D airspace". on the other hand it's been suggested that clearances for this will be given in flight, no flight plan required. is there a difference between flight "within class D" and "through class D" or is this a situation where practise has actually diverged from the rules?