Next week, Delta Air Lines will begin blocking middle seats and cutting back on the number of passengers per flight to abide by social distancing recommendations. For flights beginning April 13, middle seats in Delta's Main Cabin, Comfort Plus and Premium Select cabins will be shown as unavailable. The carrier also will pause automatic advance Medallion upgrades, instead processing upgrades only at the gate so that gate agents can best determine seating that follows social distancing practice. The changes will run through May 31.