The figure, which measures how much of an airline's capacity is filled with passengers, was 90% in July compared with 88.6% in the year-earlier month.
Revenue passenger miles rose 5.2% to 23.77 billion, while available seat miles advanced 3.5% to 26.41 billion.
In July, Delta said in a statement, its network carried 19.4 million passengers, more than it had ever served in a given month. Delta said July 8 saw more than 700,000 passengers fly with the airline's network, a daily record.
For the year through July, Delta's load factor widened to 86.3% from 85.5%.
Delta shares were trading off 1.11% at $59.65.
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