Delta Air Lines is extending eligibility and discount tiers for its corporate customers with Midmarket Sales Agreements into 2021, the carrier announced. The agreements typically come with a minimum spending amount, but Delta will determine 2021 eligibility and discounts in the program based on the company's 2019 account data. Customers who have spending levels in 2020 that qualify them for higher discount levels still will receive those in 2021, according to Delta.