Delta Air Lines reported a profitable third quarter on the gradual recovery in air travel on Wednesday, but said rising fuel prices could dent earnings in the current quarter.

"While demand continues to improve, the recent rise in fuel price will pressure our ability to remain profitable for the December quarter," said Chief Executive Ed Bastian.

The big US carrier, which endured a disastrous 2020 following a deep downturn in travel during the worst of the pandemic, said domestic travel remained a strong point in the wake of the Covid-19 vaccine release throughout the United States.

The airline also saw strength in travel to Latin America, while transatlantic travel "improved the most" during the quarter, driven by border reopenings, Delta said in its earnings release.

Corporate volumes were "stable," but the recovery in business travel paused in September as companies delayed reopening their offices due to the Delta variant of the virus.

Delta Air Lines reported a profitable quarter on the basis of increased travel demand, but said higher fuel costs could push it back into the red in the fourth quarter Delta Air Lines reported a profitable quarter on the basis of increased travel demand, but said higher fuel costs could push it back into the red in the fourth quarter Photo: GETTY IMAGES NORTH AMERICA / Michael A. McCoy

Overall, Delta reported profits of $1.2 billion in the quarter ending September 30, compared with a loss of $283 million in the year-ago period.

Revenues were $9.1 billion, up from $3.1 billion in the year-ago period, but below the $12.6 billion in 2019.

Delta anticipates fourth-quarter capacity to return to 80 percent of its pre-pandemic level on the basis of factors that include "robust holiday demand," the company said.

The carrier projected that jet fuel in the fourth quarter would be priced at between $2.25 and $2.40 per gallon, up around 20 percent from the level in the just-finished quarter.

Shares fell 4.5 percent to $41.57 in mid-morning trading.