Dr Fauci commented on vaccines earlier this week. He said to expect a vaccine that is around 60% effective. The vaccine will not eliminate coronavirus but it will be a tool to slow and control it. 60% effective is equal to the effectivity of the flu shot. I still get the flu sometimes even with the vaccine.

https://www.google.com/amp/s/www.cnbc.com/amp/2020/08/07/coronavirus-vaccine-dr-fauci-says-chances-of-it-being-highly-effective-is-not-great.html

Bill Gates, who has become something of an infectious disease expert via his foundation's work, predicts that coronavirus will be over in the rich countries by the end of 2021.

https://www.google.com/amp/s/www.cnet.com/google-amp/news/bill-gates-says-coronavirus-will-end-for-the-rich-world-by-end-of-2021/

Where does that put air t travel demand? There's no way we return to 2019 levels until covid is completely stamped out. And, the economy in general is in the toilet. Entire sectors are in freefall. Even if there was a perfect vaccine released tomorrow it would take the economy months or maybe a year to sort itself out. I'd guess we don't return to 2019 levels for three to five years or maybe even longer.

Then there's the uncertainty of future airline aid packages. American airlines could be in bankruptcy by next spring or the government could reanimate them via cares 3.0 and create a Frankenstein that destroys yields for the natural survivors. Both those outcomes are horrible but that's a choice that congress will have to make next year.