Qantas Airways Ltd could restart 40-50% of its domestic capacity in July if states relax border controls, and expects to offer low and flexible fares without social distancing measures to stimulate travel demand, its chief executive said on Tuesday.

The airline will introduce measures on board from June 12 such as providing masks and cleaning wipes to ensure safe travel and give passengers peace of mind during the pandemic, but will not leave middle seats empty.

"Social distancing on an aircraft is impractical," Qantas Chief Executive Alan Joyce told media. "It only gives you 60 centimetres (23.6 inches) between passengers."

He said to meet Australia's standard for social distancing of 1.5 metres on the ground, an Airbus SE A320 operated by low-cost arm Jetstar could fill just 22 seats, rather than the normal 180.

"That means airfares are going to be eight to nine times more than they are today," he said. "It economically will not be justified."

Instead, Qantas will simplify catering, step up aircraft cleaning and ask passengers to limit movement around the cabin once seated.

Masks will not be mandatory but Qantas will recommend passengers wear them in the interest of everyone's peace of mind, in a measure that is unlikely to be needed over the longer term, Qantas Group Medical Director Ian Hosegood said.

He said data showed the risk of catching coronavirus on a plane is extremely low and there are no documented cases of transmission, including on recent lengthy Qantas repatriation flights from London and Los Angeles that lacked social distancing.

Hosegood's comments come as jet manufacturers and airlines launch an urgent initiative to convince nervous travellers that the air they breathe on planes is safe, believing this is critical to rebuilding the travel industry.

Qantas said 98% of its frequent flyers are planning trips for when restrictions are lifted and Joyce said domestic capacity would be ramped up accordingly from the current 5% of normal.

(Reporting by Jamie Freed; Editing by Stephen Coates and Christopher Cushing)