My girlfriend has a AC ticket returning from Europe to Toronto this week: KTW-FRA-YUL-YTZ:LH has cancelled the morning KTW-FRA flight and rebooked her on the afternoon flight which misconnects in FRA. I found this out when I called LH for a different question. Neither AC nor LH notified her, which seems odd, and the bovine-information-inspector (thanks canadiancow!) still shows the original flights. The LH agent said to call AC to rebook it.

Simple enough, call AC to rebook. The complication is her situation, so I'd like to understand some options.

She is there to visit an elderly relative who is day-to-day in hospital. She will likely want to delay the return, depending on events. I'd been planning to either use AC's flexible policy if required or just book a separate cash or reward return. The cancellation turns out to be beneficial, if it lets her change the date.

This policy (AC Travel Ready Hub) says she can make a free change due to the cancellation -- does it waive the fare difference, or just change fee? It is a discount L class fare. Was there a different policy for tickets booked before Dec 31? I thought I saw posts mentioning a policy change. It is an 014 stock ticket, booked direct with AC, if it matters.

Alternatively, EU261 seems to apply, assuming they can't find a within-four-hours-arrival alternative (I can't spot one), as I found out 10 days before. EU261 seems to say she has the option to rebook on a later date, if available seats. Does the available seat need to be same fare bucket or just any seat, i.e. pay fare difference or not? Obviously they have to rebook with no fare difference if it is same date, but maybe its different if you request the date change.

The reason for asking is that while AC/LH obviously have to rebook her something, we probably want to tentatively delay the return at least a few days. But I'd prefer to avoid paying a fare difference in the meantime since it might be lower after a later change. Also we don't want to "use up" any limits in AC's free change policy, although that seems to be unlimited until Jan 31.