Delta Air Lines parked 571 mainline aircraft across the country in 2020 when the COVID-19 wiped out most passenger travel. Airlines still have about 70% of their pre-pandemic fleet in hibernation, but Delta is returning aircraft to the skies because the U.S. domestic market is recovering faster than in other parts of the world.
Parking a plane and bringing it back to life after months of inactivity isn’t as simple as turning the engines off and on. It takes a lot of effort, including maintenance...
https://www.freightwaves.com/news/how-did-delta-airlines-awaken-570-dormant-aircraft