Though The Great Recession lasted 18 months, it hit its zenith with the bankruptcy of Lehman Brothers in September 2008. Air travel fell by 20 percent from August to September.
It was only an 8 percent decrease compared to 2007, but travel had finally started recovering from 9/11. The September 2007 numbers were up 4 percent from the year prior.
The airline industry took about two years to fully rebound from The Great Recession and roughly four years to recover from 9/11.
The Great Recession dip came from widespread financial issues while the post-9/11 decline can largely be attributed to fear. COVID-19 manages to stir both of these factors together, coupled with necessary social distancing efforts — a recipe for disaster for airlines.