"More than any time in our history, the various factors currently impacting our operation -- weather and air traffic control, vendor staffing, increased Covid case rates contributing to higher-than-planned unscheduled absences in some work groups -- are resulting in an operation that isn't consistently up to the standards Delta has set," she said in a statement.
Delta will join JetBlue and Alaska Airlines, which have also cut back their summer schedule for similar reasons.
JetBlue claimed it would cut up to 10 per cent of its schedule during summer due to "continued industry challenges". Alaska Airlines pulled theirs back about 2 per cent in June to meet "pilot capacity."
The majority of Alaska Airlines' nearly 3100 union pilots voted to go on strike last week.
The timing isn't great, as 3 million Americans are estimated to take a flight during the 5-day period around Memorial Day. This statistic from AAA is 25 per cent higher than 2021.
Last week Qantas announced similar plans to lower domestic flying schedules for July and August from 107 per cent of pre-Covid-19 levels to 103 per cent.