A family member recently flew Air Canada from Venice to Los Angeles via Montreal. (If it matters, they're an EU citizen)
Due to a 3:32h delay of the original flight (VCE-YUL), they missed the connecting flight - forcing them to take a different flight on the next day and sleep in Montreal (self arranged).
They took the first available flight the next day but by that point, they arrived at their destination (LAX) 20 hours and 34 minutes late.
In the name of the family member, I contacted Air Canada asking to be refunded the hotel and food costs of the overnight stay along with EUR 600 they are entitled to based on EC 261 (Article 7 - Right to compensation).
Air Canada accepted to refund the costs connected to the delay (hotel and food), but refused to pay the penalty, claiming:
In this instance, the compensation you are requesting does not apply because the delay was caused by an event outside of our control. Specifically, awaiting a departure slot from Euro Control and further gating constraints in Montreal.
They instead offered a CAD 500 voucher as a sign of goodwill.
While I don't think they're lying, is there anywhere I can fact-check this based on the time and date of the flights?
Does their reasoning make sense, should I forget about claiming the penalty costs?