Keep an eye on the debt markets for airlines.  United have been trying to do a $2.25 billion bond deal backed by unencumbered aircraft.  Started marketing around a 9% yield and now pricing has moved coupon to 11 %.   Reflecting the markets uncertainty around residual asset value of aircraft.

United's existing bonds have plummeted and trading in the 60s.  This usually happens when equity is worthless.  For those who say this doesn't matter for AC because "it is different", recognize that pricing changes in the debt markets and the demands of the debt buyer for big deals does have knockover effects for everybody.  Look at the correlation  between debt and equity in various mkt segments.  When the Fed started buying and stabilizing bonds, equity obviously got a big bump.  

For airlines, it isn't about the equity right now , but more about the ability for airlines to refinance debt.  Keep an eye on the pricing for Air Canada's bonds.   When they bottom and turn, likely a great time to buy the equity.   Debt holders are first in line, equity holders are behind them.   If debt holders are confident about AC's future, then good picture for equity.