The simple version

Load factor is a ratio with two moving halves. On top, the seats that paying customers actually used. Underneath, all the seats the company offered, whether anyone bought them or not.

Divide one by the other and you get how full the cabin was. That is all you get. It says nothing about what any of those seats sold for.

So a company can report an identical load factor two years apart and have had two completely different years, because both halves of the ratio moved together while the prices on either side of the business moved apart.

The numbers

• Passenger load factor for the September quarter: 86% in 2026 and 86% in 2025, which the filing's change column marks as no change (Form 8-K Exhibit 99.1, Statistical Summary, filed October 9, 2026)
• Revenue passenger miles, the top of the ratio: 68,133 million against 67,621 million, up 1% (same exhibit)
• Available seat miles, the bottom of the ratio: 79,288 million against 79,054 million, which the filing marks as unchanged (same exhibit)
• Passenger revenue per available seat mile: 19.59 cents against 17.08 cents, up 15% (same exhibit)
• Cost per available seat mile: 23.63 cents against 18.96 cents, up 25%. The same table's cost per seat mile excluding fuel and certain other items the filing adjusts out rose 7.3%, from 13.08 cents to 14.03 cents (same exhibit)
• Average price paid per gallon of fuel: $3.80 against $2.26, up 68%, on 1,146 million gallons burned against 1,138 million (same exhibit)

Why the ratio can sit still while everything else moves

A ratio holds its value when its two halves move by the same proportion. Here they very nearly did: the seats used rose about 1% and the seats offered were flat, so the quotient barely moved.

Everything that is not a ratio moved hard. The money collected per seat rose 15%, the money spent per seat rose 25%, and its largest single input cost rose by about two thirds.

That is the trap in a fullness measure. It is built to be stable, and a stable number next to a volatile one invites you to read the stability as the story.

The actual math on 86 and 86

Do the division yourself. 68,133 divided by 79,288 is 85.9%. The prior year, 67,621 divided by 79,054 is 85.5%.

Both round to 86%, which is why the change column shows nothing. The real move was about four tenths of a point, lost to rounding in a table that reports money to the penny.

That rounding is the filing's, not ours, and the division is ours on the filing's own figures. One more decimal in that column would have shown the move.

What this means

If you want to know how crowded your flight will be, load factor is the right number and 86% is a crowded airplane. If you want to know why the ticket cost what it cost, it is the wrong number entirely.

For that, look at revenue per seat mile, which rose 15%, and at the cost per seat mile, which rose 25% once the price of a gallon is left in. Which of those two cost figures gets quoted decides the story being told.

Fullness and price are separate questions, measured separately, and a carrier can hold one flat while the other moves by a quarter.

What this is NOT

This article explains what load factor measures and what it does not, using the September quarter 2026 results Delta Air Lines filed on October 9, 2026 as the example. It is not a recommendation to buy, sell, or hold Delta Air Lines or any security, and it takes no view on the company's results, its capacity decisions, or its costs. It does not predict airfares, fuel prices, or what any future quarter will show. It states no figure from the release's guidance table, because the column layout could not be read reliably from the filed text, and it does not characterize the outlook as raised or cut. Nearly all of the narrative figures in that release sit inside quotations attributed to named executives, so none of them are quoted or paraphrased here; every figure above comes from the unattributed Statistical Summary. The division producing 85.9% and 85.5%, and the observation that both round to 86%, are our arithmetic on the filing's own numbers. This is not a political endorsement or criticism of anyone.

Sources

• Delta Air Lines, Inc., Form 8-K Exhibit 99.1, "Delta Air Lines Announces September Quarter 2026 Financial Results," filed October 9, 2026, accession 0000027904-26-000035, Statistical Summary