Spirit Airlines lowered its third-quarter revenue outlook to account for increased fuel prices, the ultra-low cost carrier revealed in a regulatory filing on Wednesday.

Shares of the airline were down 4.3% at $16.53 in premarket trading.

The carrier joins Southwest Airlines, United Airlines and Alaska Air Group, who have also warned of higher fuel costs in the current quarter as crude prices rose for a third straight month in August amid signs of tightening supply.

Spirit expects third-quarter revenue to be between $1.24 billion and $1.25 billion, against its previous estimate of $1.3 billion to $1.32 billion.

However, the company sees "heightened promotional activity" with steep discounting for travel booked for the second half of the third quarter through the pre-Thanksgiving travel period.

Spirit now sees third-quarter per-gallon fuel costs at $3.06 against the earlier guidance of $2.80.

(Reporting by Pratyush Thakur in Bengaluru; Editing by Mrigank Dhaniwala)