EU rights when flight delayed so much that return is missed

The other question already covers the 5 hour delay so I will not repeat that part here, but I assume you’re also interested in smaller delays (in case of 2h meeting, a 2-3h delay is enough to ruin your agenda and make the travel pointless).

While such situation are partially covered by the EU regulation, you also have to consider tort law. The latter may not be uniform across the EU so you need to check for more details for a specific case.

The EU regulation stands that if your flight is delayed for over 3h (in case of connecting flight the arrival to the final destination counts) then you are eligible for a compensation. The amount varies from 125 to 600 EUR depending the delay time (below 5h it can be reduced by half, the amount for shortest flights – most intra-European – is 250, for the longest ones, all outbound it’s 600). You’re also eligible to some (limited) assistance.

This page about passenger rights within EU gives more details.

In addition to the EU regulation some national laws may give you additional rights. For example Polish tort law states that the company will be liable for any loss, however you need to be able to directly specify such loss. So if you cannot attend the meeting due to delay, your employer is eligible to request compensation for your time and other expenses associated with your trip. They cannot however claim a compensation for a potential loss (e.g. if you were flying to negotiate with the potential client and the negotiation did not take place you cannot claim the expected contract earnings, however if you had to pay some fine for not showing up on the meeting, that’s reimbursable).

An airline might not be too willing to accept such claims in which case you may need to file the case to a court.

Not related to flights, but to trains (so very similar situation, there are also EU regulations about that) – when my train was delayed by 2 hours making it plausible that I will miss my plane, I’ve decided to catch a taxi at one of the stops (yes, taxi was faster) and go directly to the airport. Of course EU regulation doesn’t cover that. I barely managed and claimed for the reimbursement of the taxi cost (some 35-40 EUR). It took me 3 months and a few formal letters but they eventually reimbursed the whole amount (even though they officially stated that they rejected my claim and that they pay this amount as an exception).

The flights are on the same ticket, so the airlines should make sure you can take all flight (else they are actively blocking you to fulfill the travel contract).

The EU right allow you to cancel the flight and get full refund, in case of delays (instead of compensation). This has few rules, but it should be better than flying and returning without exiting the airport. I think you should prefer such option, when you see that the outbound flight is so delayed.

Reimbursement and a return flight in the event of a long delay (5 hours or more) at departure

If your flight is delayed at least 5 hours at departure, the airline must reimburse your ticket and, if you have a connecting flight, offer a return to the airport of departure at the earliest opportunity.

If you have less then 5 hours, it could be tricky (but 2 hour meeting, 1 hour buffer on both arrival and departure, and some time to reach the meeting), this could be the case.

This answer the question in the middle of your text.

The main question is interesting, and it is difficult to tell. The EU regulation defines the final destination as:

‘final destination’ means the destination on the ticket presented at the check-in counter or, in the case of directly connecting flights, the destination of the last flight; alternative connecting flights available shall not be taken into account if the original planned arrival time is respected;

so in theory this final destination should be your home airport, but this will make most of the rules non-sense, and contrary to the purpose of compensations.

I think with long delay and short flights, you should ask at gates for alternative. I think in such case they could help more: It is their interest (with long delay, the probably outcome is to cancel the flight and to get people in the next flights [if there are several flights per day, like the case in the question], so having less passengers relives them from compensations and cost to other airlines.

ADDENDUM: It was marked very prominently and on the TOP on EU passenger right:

The outbound and return flights are always considered as two separate flights even if they were booked as part of one reservation. In some cases the airline operating the flight (also known as the operating air carrier) may not be the same as the one from which you bought your ticket. In case of any difficulties only the airline which operates the flight can be held responsible.