The article also completely misunderstands what forecasting is. Of course you cannot give precise figures for such things, but you are not attempting to. I happened to have had a little involvement in the decision whether to build Terminal 5 at Heathrow. Does anyone imagine such a decision was taken without forecasts of the number of passengers, goods, etc? Does anyone imagine a power station is built without forecasting the demand? Any of those forecasts could be out in detail, or quite substantially - what Brexit will or will not do to passenger traffic was not modelled for instance - but you take the decision using the best information you can, while simultaneously recognising its limitations.