I've also successfully taken airlines through the court system, and along the way I read up on the relevant cases - which took me quite a while. Now by the time someone has done their homework, you are probably in a better position to know whether you're on thin ice or not, indeed you will typically know more about it that the junior solicitor assigned to the case by the airline. And now there is a high degree of consistency about the whole matter.

So in broad terms weather and strikes are extraordinary circumstances (but not "knock on" consequences 3 days down the line). Technical failures of a standard type are not extraordinary (cracked windows for example), however airlines try to argue the more esoteric case. There is a key test here: could the airline reasonably done something to have prevented the incident? Fog this morning in LHR - unlikely. Defective pump requiring a spare part - far more arguable. There is a random element: District Judges bring their own common sense to cases, and small claims judgements are deliberately intended to stand on the very precise merits of the case, rather than setting case law.

Having read the new preliminary judgement I think there are 2 key things that were new (to me at least): firstly some emphasis on what action the airlines themselves can take in this situation. So I predict a greater willingness of airlines to re-route passengers onto other airlines as the least cost option; BA and other airlines used to hesitate on this aspect. Secondly a point made in the preliminary judgement that 99.85% of trips are unaffected by delays covered by the Regulation.

If you have to fight the airlines to get compensation, you're not going to regard the €400 (or whatever) as worth the 4 hour wait - it really is a lot of hassle.