Delta assumed the deal as part of its merger with Northwest Airlines in 2008 (which set it back $2.6bn in shares), though in 2010 it deferred the order to a "2020 and beyond" delivery timetable.
Though it did not disclose the specific terms of the agreement, in a statement Delta said it will continue to take delivery of new 737-900ER aircraft through to 2019, as two orders that total 120 aircraft remain outstanding.
"Delta is one of the world’s largest operators of Boeing aircraft and our valued partnership with Boeing will remain strong as we safely and comfortably serve our customers across the world every day," said Greg May, Delta's senior vice president of supply chain management and fleet.
"This business decision is consistent with Delta’s fleet strategy to prudently address our widebody aircraft needs."
The cancellation comes as Delta and other top US airlines seek to slow flight capacity growth and in some instances shrink existing service in response to falling airfares.
Earlier this month, President-elect Donald Trump took aim at Boeing for its expensive Air Force One contract, saying he thought the costs were "ridiculous".
In March, the aircraft maker announced plans to cut up to 10 per cent of its workforce, around 4,000 jobs, and just before Christmas announced it will start a voluntary layoff programme in its commercial aircraft unit next year.