At what price per barrel, will airlines simply refund tickets?

So, I'm looking at the oil crisis and wondering. What price per barrel of oil would we see major shutdowns of flights? My logic is there will be a certain price per barrel of oil where the cost of flying the plane from one place to another will simply be more expensive than the ticket revenue?

I get that before we get there we'll see airlines working together to reduce the number of flights between locations, but at some price point (for example 5k per barrel) the company would just refund the tickets and be like, Nah man.