On the eve of Black Friday, the official start of the holiday shopping season, pilots for a regional Ohio cargo airline that delivers packages for Amazon and DHL went on strike. This could cause delivery delays.

ABX Air, a unit of Air Transport Services Group, said it would try to end the strike by seeking a court order and get the roughly 250 pilots back on the job.

ABX Air operates 45 daily flights for DHL and 35 for Amazon. All were canceled Tuesday.

Because pilots won't cross picket lines, planes can not leave the Amazon hub in Wilmington, Ohio, (southeast of Dayton,) or the DHL hub in Cincinnati, according to the Wall Street Journal.

Amazon, which dominates e-commerce sales, has a big presence in Ohio, where it's building three data centers and two warehouses, according to the Columbus Dispatch. The newspaper says Amazon will invest $1 billion in the state.

Amazon told Bloomberg it works with many carriers, and was confident it would be able to get packages to customers.

Between the two clients, DHL and Amazon accounted for 65% of Air Transport Service's revenue in the third quarter, according to the AP.