United Airlines on Wednesday said its third-quarter net income fell slightly less than investors had feared as the third-largest U.S. carrier was hit by US$185 million in pretax losses caused by cancelled flights during the Atlantic hurricane season.

Its shares edged up slightly in after-hours trading.

The Chicago-based carrier said passenger revenue per available seat mile, a closely watched measurement of an airline's performance, fell 3.7 per cent, about 1 percentage point of which was attributable to disruptions caused by storms.

For the current quarter, United forecast that passenger revenue per available seat mile would decline by 1 per cent to 3 per cent.

In addition to the impact from unusually severe storms this season, United has been hurt in recent months by an increasingly competitive fare war in key markets against low-cost carriers like Spirit Airlines Inc and Frontier.

United has acknowledged the short-term impact on profit from matching sharply discounted fares against its competitors, but has said it would continue matching fares until it could outpace low-cost rivals.

For the third quarter, United posted a quarterly pre-tax margin of 10.4 per cent and said it expects to have a pre-tax margin of between 3 per cent and 5 per cent in the fourth quarter.

It reported net income of US$637 million, down 34 per cent from US$965 million in the year-ago quarter.

Excluding some special charges, United reported earnings per share of US$2.22 per share. That beat Wall Street's average forecast of US$2.16, according to Thomson Reuters.