Airlines are blocking middle seats. Delta has stopped processing upgrades in advance, handling all upgrades at the gate, to manage seat assignments in domestic first class so that passengers aren’t seated beside each other. They’re also blocking seats near flight attendant jump seats, to keep passengers away from flight attendants.
These are all social distancing steps to limit contact between people during travel, both to help stop the spread of the coronavirus and also to give customers confidence to fly. But they won’t do this if it means losing even a single ticket sale.