I'm not sure, but I'd bet that it has to do with $$$.

That's what I was getting at.....is only 150ft. of a 200 ft. wide runway "weight bearing"?

I know that the FAA, or whatever body decides standards and requirements, is allowing the A380 to land on a 150ft. wide runway as long as other modifications are made (apron improvements, taxiway widths, lighting changes, jetway additions, etc).

But  is a 200ft. wide runway simply a 150ft. wide runway with "extra dressing"?

I think these are really the generic reasons why:

The cost. If you can't afford a larger runway, then you'll have to settle for small.

Airfield. Small airfields need small runways. Something like London City airport will need a smaller runway... Their runway is under 100ft wide.

Demand. Why build a super runway if you're only going to be handling business jets and small trainers?

Age. An older runway is probably a smaller runway. And that goes back to the above points... Particularly in the UK a lot of airfields are built-up versions of WW2 runways. Their aircraft were smaller and didn't require a massive runway.


For this particular question though, I would put it down to cost. If they don't need a big runway, they won't buy one. Some airports may look to future-proof their airfield, others will upgrade when required.