U.S. airlines reported lower traffic in October than a year ago, but their seats are more than 80% full because they've cut capacity throughout the year.

Delta Air Lines says its October traffic -- measured in revenue passenger miles, or the number of revenue-paying passengers multiplied by the distance traveled -- fell 3.8%. Its domestic traffic fell 1.6%. But the carrier's load factor -- or the percentage of capacity used -- fell by only 0.6 percentage points to 82.8% because it cut capacity by 3.1%. Domestic load factor rose 1.3 points year over year to 84.3%. Delta flew 13.9 million passengers in October.

American Airlines says its traffic fell 1.1%, with domestic traffic volume down 1.8%. The carrier's load factor for October fell 0.3 percentage points from a year ago to 83.2% as it cut capacity by 0.7%. American boarded 7.2 million passengers in October.

US Airways says its October mainline traffic fell 1.5% from a year ago. The carrier also reduced capacity by 1.7%, leading to a 0.1 percentage point increase in load factor to 83.7%. It flew 4.4 million passengers in October.

Alaska Airlines, one of the few airlines to add capacity, reported a 6% increase in traffic in October. Its capacity grew by 5.1% from a year ago. Its load factor rose by 0.8 points to an October record 82.6%.