I do not think you can get to 17 hours for unforeseen circumstance unless you are augmented.
Unforeseen Operational Circumstances — Flight Duty Period and Rest Period
700.63 (1) If the pilot-in-command is of the opinion that an unforeseen operational circumstance that occurs within 60 minutes of the beginning of the flight duty period could lead to a level of fatigue that may adversely affect the safety of the flight, the pilot-in-command may, after consulting with all crew members on their level of fatigue,
(a) reduce a flight crew member’s flight duty period;
(b) extend a flight crew member’s flight duty period by the following number of hours in excess of the maximum flight duty period set out in section 700.28 or subsection 700.60(1) by
(i) one hour for a single-pilot operation,
(ii) two hours, if the flight crew is not augmented,
(iii) three hours, if the flight crew is augmented and there is one flight during the scheduled flight duty period, and
(iv) two hours, if the flight crew is augmented and there are two or three flights during the scheduled flight duty period; or
(c) extend a flight crew member’s rest period.
(2) If a further unforeseen operational circumstance arises after take-off on the final flight for which the maximum flight duty period was extended under subsection (1), the pilot-in-command may, despite that subsection, continue the flight to the destination aerodrome or to an alternate aerodrome.
(3) An air operator shall extend the rest period after a flight duty period is extended under this section by an amount of time that is at least equal to the extension of the flight duty period.
(4) At the end of a flight duty period, the pilot-in-command shall notify the air operator of any change to a flight duty period made under this section.
700.28 (1) An air operator shall not assign a flight duty period to a flight crew member, and a flight crew member shall not accept such an assignment, if the flight duty period exceeds the maximum flight duty period set out in this section.
(2) If the average duration of all scheduled flights is less than 30 minutes, the maximum period of a flight duty period that begins during a period set out in column 1 of the table to this subsection is the number of hours set out in column 2, 3 or 4, according to the number of flights scheduled during the flight duty period.
TABLE
Maximum Flight Duty Period — Average Flight Duration of Less Than 30 Minutes
Column 1 Column 2 Column 3 Column 4
Item Start Time of Flight Duty Period 1 to 11 Flights 12 to 17 Flights 18 or More Flights
1 24:00 to 03:59 9 hours 9 hours 9 hours
2 04:00 to 04:59 10 hours 9 hours 9 hours
3 05:00 to 05:59 11 hours 10 hours 9 hours
4 06:00 to 06:59 12 hours 11 hours 10 hours
5 07:00 to 12:59 13 hours 12 hours 11 hours
6 13:00 to 16:59 12.5 hours 11.5 hours 10.5 hours
7 17:00 to 21:59 12 hours 11 hours 10 hours
8 22:00 to 22:59 11 hours 10 hours 9 hours
9 23:00 to 23:59 10 hours 9 hours 9 hours
https://lois-laws.justice.gc.ca/eng/reg ... l#s-700.13