Qantas has posted a full-year underlying pre-tax loss of $1.86 billion after border closures and travel uncertainty as the COVID-19 pandemic weighed on earnings.

The airline's net loss after tax for the year to June 30 narrowed to $860 million, compared to $1.7 billion the year before.

"These figures are staggering and getting through to the other side has obviously been tough," chief executive Alan Joyce said on Thursday.