Nationwide unrest in Kazakhstan forced foreign airlines to suspend flights to Almaty in January 2022, testing how quickly carriers reassess geopolitical risk.
Thousands of flights were cancelled around Christmas 2021 as the Omicron variant left airlines without enough healthy crew.
When the US reopened its borders to vaccinated travellers on 8 November 2021, airlines saw an immediate and dramatic surge in international bookings.
American Airlines cancelled nearly 2,000 flights over Halloween weekend 2021, blaming storms in Texas and a shortage of crew.
In September 2021, United Airlines became the first major US airline to fire staff who refused its COVID-19 vaccine mandate.
In the summer of 2021, Spirit Airlines cancelled thousands of flights and left passengers stranded across the United States.
