US airline Frontier wants to charge passengers up to $138 to social distance

Frontier Airlines said it's going to charge extra for passengers who want to guarantee a spot next to an unoccupied middle seat in the age of social distancing.

The carrier aims to generate revenue on the empty seats, charging from $US39 to $89 ($A60-138) depending on the route. It will have 18 "More Room" assignments available on each flight from Friday through August 31, spokeswoman Jennifer De La Cruz said Monday.

The new product complements a face-covering mandate Frontier is imposing for passengers starting Friday to help guard against the spread of the new coronavirus, along with a "health requirement" customers must accept before they can check in for a flight.

As part of that new system, Frontier travellers must check their temperature, attest that neither they nor anyone in their household has exhibited Covid-19 related symptoms for 14 days and wash their hands or use sanitiser before boarding a flight on Denver-based Frontier, which is owned by private equity firm Indigo Partners.

Large carriers such as American Airlines and Delta say they've begun blocking many middle seats to promote greater distance among passengers. The airlines don't guarantee a middle seat will be unoccupied and they generally may assign them as needed.

Last week, American said it would sell only half the middle seats available in its economy cabin, though it will assign those seats when necessary. Southwest Airlines is also limiting its seat sales to promote greater spacing but did not specify by how much.

"We are well aware that all airlines, Frontier included, are making efforts to allow people to spread out," De La Cruz said in an email. "But the opportunity for those measures will taper off as more people start flying."

Ultra low-cost airlines such as Frontier, Spirit Airlines and Ryanair generally need to sell more of their seats to break even than do larger airlines that have more frills that generate revenue and generally higher fares.

Last month, Ryanair Chief Executive Michael O'Leary said his airline - which has suspended most of its flights - would not resume operating if government regulators require empty middle seats that can't be sold.