America's Delta Air Lines, Inc. has added 460 names to its no-fly list - typically reserved for suspected terrorists. The people added had refused to comply with the company's mandatory mask policy for flights.

Delta's chief executive officer Ed Bastian explained the decision to staff in an internal memo. Bastian reminded employees of the importance of awareness and the implementation of "multiple layers of defense" to combat the increase in COVID-19 infections.

"Throughout the pandemic, we have focused our efforts on protecting our people, our customers and our communities...Wearing a mask is among the simplest and most effective actions we can take to reduce transmission - which is why Delta has long required them for our customers and our people," Bastian said.

There have been several incidents of Delta flight crews confronting passengers because of their refusal to wear masks. On Saturday, a Delta flight to Las Vegas was delayed for more than 90 minutes after one passenger refused to wear a mask and became involved in an argument with crew. Earlier in October a crew member was struck in the face by a passenger who refused to wear a mask. This incident was recorded and later went viral after being posted online.

There have been similar incidents in the past and the airline said it needed to implement measures to refuse service to those unwilling to comply. In June, large U.S. airlines agreed to impose mandatory mask-wearing on all flights.

The policy has remained in effect in the absence of any new regulations and orders from the federal government and the Centers for Disease Control and Prevention. Despite the altercations and confrontations, airlines have defended their mandates as vital to protecting both passengers and crew.

The Centers for Disease Control and Prevention issued guidance in October stating that traveling at this time posed an increased risk of people contracting the virus. The agency said those that needed to travel should wear masks and other protective gear.