Upvote:5
Turkish airlines is known to be fairly "variable" when it comes to things like this, and the outcome often depends on the actual person checking you in rather than any formal policy.
Even their own website is confused as to the correct procedure, claiming in the section "International transfer passengers (flight routes issued on separate ticket) continuing to a foreign destination with another airline" that you need to BOTH collect your bags (which would require going through immigration), and remain airside and go to the transfer desk (which will not result in your baggage being transferred).
Officially their policy appears to be that they do NOT interline baggage (ie, check it through to the final destination) in cases like this - however this seems to be at the liberty of the actual check-in agent.
However in this case you have an additional complication - a layover of 17 hours is beyond the normal 12 hours that Turkish seems to ever allow for interlined bags so I'd say it's very unlikely that they will allow it.
Further adding to the complication, Turkish Airlines will not be able to issue a boarding pass for the Air Canada flight - leaving her to get one at the transfer desk in Istanbul. However as AC only has one flight per day to Istanbul (the one she is one), their transfer desk will probably not be open at the time she arrives which means that she will be stuck in the arrivals area for probably 12+ hours - and as far as I remember there are no facilities (food, etc) in that part of the airport... She may be able to get around this with online check-in - I'm not sure of AC's policies on online checkin when visas are involved.