If your ticket is a round-trip, if you do not fly the outbound leg KL rebooked you on, the whole trip will be cancelled.
Remember your rights (
https://europa.eu/youreurope/citizen...ncellation-1):
If your flight is cancelled, the airline must offer you, on a one off basis, a choice between:
- the reimbursement of your ticket and, if you have a connecting flight, a return flight to the airport of departure at the earliest opportunity
- re-routing to your final destination at the earliest opportunity or,
- re-routing at a later date at your convenience under comparable transport conditions, subject to the availability of seats.
As soon as you have chosen one of these three options, you no longer have rights in relation to the other two options. However, the airline carrier may still have to provide compensation
- if you choose to have your ticket reimbursed – the compensation will depend on the type of flight
- if you choose re-routing – compensation will depend on the type of flight and the delay in reaching your final destination, past the original scheduled arrival time.
You could choose between two options with KL:
- Option #1: ask for reimbursement of your original ticket. Then buy your new ticket by yourself. KL will still have to provide compensation.
You will end with: reimbursement of the original ticket + 600€ cash compensation or 800€ voucher - cost of the new ticket
Be careful, if your ticket is a return ticket, your whole trip will be canceled/reimbursed. Do not buy a single trip IAH->AGP and expect to fly back to IAH with your original ticket, it will not be possible.
- Option #2: insist on being rerouted. The EU regulation states that KL must reroute you "at the earliest opportunity". Airlines often try to believe it means "at the earliest opportunity on one of their flights" but that is not what is written. If you could find a open seat on an earlier flight, the airline must reroute you via this flight. Dura lex sed lex.
You will end with: 600€ cash compensation or 800€ voucher - cost of the new ticket you will not use
As you have already accepted a rerouting on AA you don't want to use, I would suggest you do not request any refund online (except if the website is clear enough) but call an agent instead to be sure the cancellation is made through EU261.
In any case, KL is due to pay you the compensation. If you just don't take the flight tomorrow, KL will not reimburse the flight though and the upcoming legs of your original ticket will be cancelled. If you cancel the ticket (= whole ticket, not just the outbound flights), you may be refunded (but it may be too late as you have already been rerouted) and receive the compensation.