US carrier Delta Air Lines will continue to block the sale of middle seats and cap the number of passengers on flights through to the end September.

Delta introduced the cap on passenger numbers after passengers on some US carriers reacted to lack of social distancing on flights by posting photos and videos of crowding on social media.

US carriers have continued to operate domestic services throughout the Covid-19 crisis, in part as a condition of US federal aid.

Delta confirmed this week: “Delta is extending our commitment to make more space for safer travel by continuing to block the selection of middle seats and capping seating in every cabin through to September 30.

“We continue to block middle seats. All middle seats will continue to be shown as unavailable or not assignable when selecting seats via the Fly Delta app or online.”

It also pledged to “sanitise every flight at every Delta airport using electrostatic sprayers”.

Airline association Iata and leading carriers have argued against leaving middle seats on aircraft empty, claiming it is both uneconomic and unnecessary given the effectiveness of high efficiency particulate air (HEPA) filters on modern aircraft.

Ryanair has also ruled out sanitising aircraft between flights.

But Delta chief customer experience officer Bill Lentsch said: “Reducing the number of customers on every aircraft across the fleet is one of the most important steps we can take to ensure a safe experience for our customers and people.”

The carrier pledged: “Delta will ensure more space for customers on all aircraft by capping seating at 50% in First Class, 60% in main cabin, Delta Comfort+ and Delta Premium Select, and 75% in Delta One [business class] to reduce the total number of customers on board.” said it would also continue to block some aisle seats on smaller aircraft.

Delta said it would also block some aisle seats on smaller aircraft.

The carrier announced it would add flights or upgrade to larger aircraft “on routes where increasing customer demand is driving flight loads closer to our caps.”