I called recently, because I am affected by cancellations. I asked about the open ticket. The call center agent informed me, after speaking to her supervisor, that I can use the open ticket for a flight in the future, within one year of booking date for any flight (can even change the airport) within the same booking class (in this case business, I don't mean A, Z, D etc.) with no fare difference or other fees. I asked if I could use the flight in the summer and she said yes. That's way better than a voucher. She even offered a refund (or voucher), but since I will fly within the next year.. I just need to keep the booking code and she made a note so in a future call, the next agent can read it and won't ask for any fees/fare difference. Quite generous and a good solution in my eyes. I probably won't wait until summer to make use of it.