As a result of the changes, Delta said it will also halt automatic advance upgrades for elite-level frequent fliers.
Aircraft safety requirements for weight and balance of the plane also affect seat assignments. Flight attendants can help passengers find a new seat where weight-and-balance restrictions allow it, if it's within three rows and in the same class of service, according to Delta.
Delta said April 14 that it will have the new seating policies in place through June.
The airline also said it is boarding customers by row, from back to front to reduce the need to walk past other passengers who are seated. It is also reminding them to allow extra space while boarding.
And, Delta is expanding temperature screenings of employees across its system. It had already begun screening temperatures at its Atlanta headquarters.