Delta Air Lines (DAL) reported third quarter results on Friday morning that missed the mark, as strength from Delta's premium business could not blunt the effects of higher fuel prices. Delta subsequently cut its guidance, noting that its total fuel bill for the year would increase by a whopping $6 billion.

For the quarter, Delta reported Q3 adjusted revenue of $17.58 billion, slightly below analyst estimates of $17.76 billion per Bloomberg, up 15.7% from a year ago. Delta posted adjusted earnings per share (EPS) of $1.72 vs. the $1.82 estimate, and adjusted net income of $1.134 billion vs. the $1.23 billion expected.

Delta said its Q3 performance was hit by $500 million in higher fuel costs than the guidance it issued in July. Delta's total fuel bill for the quarter hit $4.1 billion, up 62% from a year ago, as the US-Israeli war with Iran rocked the global oil market.

Read more: How oil price shocks ripple through your wallet, from gas to groceries

Delta stock was down over 1% in premarket trading.

Speaking of guidance, Delta cut its adjusted EPS forecast to $5.10-$5.60 from $6.50-$7.50, with its free cash flow forecast coming down to $2.5 billion from a range of $3 billion to $4 billion.

"For the full year, we expect to generate a pre-tax profit of roughly $4.5 billion, absorbing a $6 billion increase in fuel costs," CEO Ed Bastian said in a statement. "Looking ahead, our focus remains on profitable growth and delivering against our long-term financial framework, including mid-teens margins and returns, durable free cash flow, and gross leverage of approximately one times."

"All of it's fuel," CFO Erik Snell added when asked where the impact of the guidance cut came from on a call with reporters. Snell added that he expects fuel costs to be higher next quarter as well, but Delta is planning to grow capacity by 2%, a reversal from earlier this year.

It was Delta's highest-spending customers who helped blunt some of the blow this quarter.

Delta's premium business grew 18% year over year in Q3, with loyalty and related revenue up 18% as well. American Express (AXP) credit card remuneration grew 15% from a year ago, on track to "exceed $9 billion" for the year, Delta said.

Read more: Delta SkyMiles® Gold American Express Card review

A lie flat seat in a Delta One cabin. · Delta

Part of the reason Delta's premium segment is so strong is the perceived benefits of higher service and better loyalty treatment that Delta's SkyMiles members expect. However, one area that's been a thorn in the airline's side is in-flight wifi.