Delta Air Lines posted its biggest-ever September-quarter revenue on Friday, but the record top line came with an asterisk: a jet-fuel bill that blew past $4 billion wiped out nearly half the airline's bottom-line profit and forced executives to slash their full-year earnings forecast by roughly a quarter.

The Atlanta-based carrier reported GAAP revenue of $20.2 billion for the three months ended September 30, up 21% from a year earlier, according to Delta's filing with the Securities and Exchange Commission. On an adjusted basis, revenue hit a record $17.6 billion, up 16%.

But profit told a very different story. Net income sank to $756 million from $1.4 billion a year earlier, a drop of roughly 47%, as the Atlanta Journal-Constitution reported. GAAP earnings per share fell to $1.15 from $2.17. On an adjusted basis, the figure Wall Street watches most closely, Delta earned $1.72 a share, essentially flat with last year but short of the $1.92 analysts had expected, according to an earnings-call transcript published by Investing.com.

Fuel Is the Culprit

The gap between record revenue and shrinking profit comes down to one line item: jet fuel. Delta's adjusted fuel expense climbed to $4.14 billion, up 62% from the same quarter last year, with the average price per gallon rising to $3.61, even after a 13-cent-per-gallon cushion from the airline's own refinery. The refinery, a rarity among U.S. carriers, is expected to contribute roughly $700 million in profit for the full year, partly blunting the hit.

Executives tied the resilience in revenue to still-robust travel demand, particularly in premium cabins and among corporate accounts. Chief Commercial Officer Joe Esposito said the week after Labor Day was the highest corporate sales week in company history, and Delta highlighted an eighth consecutive quarter of double-digit growth in SkyMiles credit card spending.

"OUR RESULTS DEMONSTRATE THE STRUCTURAL DURABILITY THAT WE HAVE BUILT."

That was CEO Ed Bastian's framing on the earnings call, as he pointed to a return on invested capital he said was "well above cost of capital and moving towards 15%."

Still, the fuel squeeze was enough to push Delta to cut its guidance. The company now expects full-year adjusted earnings of $5.10 to $5.60 a share, down sharply from the $6.50-to-$7.50 range it had reaffirmed as recently as July, and full-year pre-tax profit of about $4.5 billion, down from roughly $5 billion in 2025, according to the SEC filing and the Journal-Constitution's reporting. Delta said it is absorbing a $6 billion increase in fuel costs for the year overall.

Shares slipped in early trading, falling about 2.1% to $80.41 from Thursday's $82.14 close, a relatively muted reaction given the size of the guidance cut, suggesting investors had already priced in a tougher fuel environment.

Context matters here too: domestic airfares were up 23.4% year-over-year in August, per Bureau of Labor Statistics data cited by the Journal-Constitution, with reduced competition since budget carrier Spirit Airlines ceased operations in May adding to pricing power across the industry.

Looking ahead, Delta is guiding to a 20% revenue jump in the December quarter alongside roughly 3% capacity growth, with per-share earnings of $1.15 to $1.65. The carrier also plans to pay down more than $2 billion in debt this year and said it expects fuel costs to eventually ease, though CFO Erik Snell did not commit to a timeline. For now, the airline that built its own refinery to tame fuel swings is learning that even that hedge isn't enough to keep rising jet-fuel prices off the bottom line entirely.