A pilot who was only on a flight from Toronto to Newfoundland via Air Canada because he was flying from the country’s eastern province as a next gig, had to step in and land a plane when the original first officer became incapacitated. The pilot was known as a deadhead. That is, he was only being relocated from airport to airport to make his next assignment.

https://www.msn.com/en-ca/travel/news/off-duty-pilot-saves-the-day-lands-plane-after-original-pilot-became-incapacitated/ar-AA1d0EN4?