Upvote:2
You could use Google Flights for this. They offer price alerts for specific flights or routes. From their documentation:
- Go to Google Flights.
- At the top, choose the number of stops, cabin class, and how many tickets you need. Choose your departure airport and destination.
- To track prices for this route, turn on the switch next to "Track prices."
- Optional: To track prices for a specific flight, choose your flights, then click Track price.
This service is worth looking into in general, there are many other very useful features in there.