The bureau said U.S. airlines' service load factor dipped to 83.9 percent. The load factor is measured in revenue passenger-miles (RPMs) or passengers that produced revenue, and is considered against the total available seat miles. The all-time high was reported in October 2015, at a seasonally adjusted 84.9 percent.
Seasonal adjustments are made to eliminate annual shifts when short-term analysis is required.
The report said systemwide RPMs for January came in at 76.5 billion, approximately 0.5 percent less than October's total.
The data that is used in these statistics is collected from 75 air carriers operating in the U.S. and is based on monthly reports filed with the BTS. February traffic data is expected to be released on May 12.