The Anchorage and Fairbanks international airports had more growth than expected in 2015, with much of the increase in cargo traffic caused by stalled ports along the West Coast.

Last year, Ted Stevens Anchorage International Airport and Fairbanks International Airport -- which together make up the Alaska International Airport System -- saw combined growth of more than 6 percent from 2014, measured in both the number of passengers boarding airplanes and the maximum takeoff weight of passenger and cargo planes, according to a report released this week by the Alaska Department of Transportation and Public Facilities.

That exceeded anticipated growth "by several percentage points," the report said.

For air cargo, problems at ports in the Lower 48 largely drove that increase.

Specifically, Anchorage airport manager John Parrott said, the labor dispute that nearly shut down the ports of Los Angeles and Long Beach in California, Seattle and Tacoma in Washington and others along the West Coast were behind the bump in Alaska air cargo numbers. That dispute between the International Longshore and Warehouse Union and the Pacific Maritime Association over contract negotiations led to massive delays in unloading ships in early 2015.

For that reason, Parrott said he's careful not to get too excited about the numbers.

"I'm very cautious about looking at 2015 and saying, 'We're back on track,'" Parrott said. "Without what we perceived to be a bump from the labor issues, 2015 was going to be a stable to maybe small growth year for cargo, but it wasn't going to be a 6 percent bump."

Air cargo has declined in recent years at the Anchorage airport.

The report said moderate growth of 1 percent to 2 percent is expected for 2016 in both passenger and all-freighter cargo traffic.