"Since the beginning of 2020 we've refunded over 11 million tickets totaling $6 billion, of which 20% has taken place in 2022," Bastian wrote Transportation Secretary Pete Buttigieg in a letter made public Wednesday.

He also disclosed Delta automatically deposited an extra 10,000 miles in the frequent flyer accounts of travelers who experienced travel interruptions between May 1 and July 7.

(Reporting by David Shepardson; Editing by Chizu Nomiyama)