Two passengers were removed from a flight about to take off because they refused to wear a mask.
The duo were ejected from a Delta flight after they failed to follow the strict rule requiring travellers to cover their face at all times.
The plane was set to fly to Atlanta, but the departure was delayed before it could leave Detroit Metro Airport.
A spokeswoman said: “Flight 1227 from Detroit to Atlanta returned to the gate following two customers who were non-compliant with crew instructions.”
“After a short delay, the aircraft departed to Atlanta.”
Delta has introduced strict measures designed to curb the spread of coronavirus while flying.
Last month, it said travellers who cannot wear a face mask for health reasons must undergo a medical screening before flying.
And it said it encouraged people to “reconsider travel” if they cannot wear a mask – as the pandemic continues.
The airline’s website states: “Delta customers and employees are required to wear a face mask, or appropriate cloth face covering over their nose and mouth throughout their travel, aligning with best practice guidelines from the CDC.
“Plastic face shields may be used in addition to a mask but are not approved mask replacements.
“Any mask with an exhaust valve is not approved as an acceptable face mask for customers traveling on any Delta operated flight.”
Face coverings have become mandatory for most travellers globally, with all major UK airlines asking people to cover their face.
In countries such as Spain, it is also illegal to not wear a face mask while on public transport for anyone over the age of six years old.
Since June 15, face coverings have been required while using public transport in England.
On July 22, Delta CEO Ed Bastian said passengers who refused to wear masks would be banned from flying with the airline.
He said: “You cannot board a Delta plane unless you have a mask on.
“If you board the plane and you insist on not wearing your mask, we will insist that you don’t fly Delta in the future.
“We already have over 100 people we’ve put on that list.”
On August 3, Delta announced it was restarting its flagship route between London and New York.
Capacity has been reduced and the airline has blocked off all middle seats on flights to ensure social distancing rules can be followed.
Roberto Ioriatti, Delta’s vice president transatlantic, said: “We know how important it is for our customers to feel safe when they fly. It’s always our number one priority and even more so during this time.
“This is why, as we add more routes between London and the US, we’re continuing to limit the number of people per aircraft.
“We are also offering additional flexibility with tickets, so customers have extra peace of mind should they need it. ”