Originally Posted by funkydrummer

IANAL. EC261 is a HUGE mess. For instance, the law is NOT explicitly saying that a delay of 3+ hours (not caused by extraordinary circumstances) entitles you to compensation. Instead, it was an ECJ ruling from 2009 (?) which declared that such a delay is equivalent to a cancellation with regards to compensation. Even more so, the regulation doesn't even define what is an "extraordinary circumstance", courts had to define that, too. Those are just two examples of the vast incompleteness of that regulation.

It has been left to the courts to decide which schedule changes are to be treated analogously to a cancellation (article 5 covers the latter). My understanding is that a substantial schedule change gives you the rights of article 8 (reimbursement and, if applicable, return to point of origin, re-routing at earliest opportunity, or re-routing at the convenience of the pax) in several countries to which EC261 applies. And article 5 of EC261 gives an orientation as to what is substantial, which is then extrapolated outside the realm of compensation. So some federal courts have ruled that, for example, a -2h schedule change you were informed about, say, 21 days before departure, gives you the right to reimbursement. (Obv, no compensation as you were informed 14+ days in advance.)

EDIT: I guess it's a little more than "my understanding is". I've won cases vs. several airlines in this regard using a lawyer from Berlin. Like, LH, FR, or IB refusing to rebook on another carrier after a schedule change. So I requested a rebooking on another carrier, setting a time limit. They usually don't react or offer an unacceptable change on their own metal. You have to rebook on your own dime and get your money back in court.