A pilot strike is threatening to ground flights carrying cargo for Amazon during the busy holiday season.
About 250 pilots employed by ABX Air, a subsidiary of Air Transport Services Group Inc., went on strike Tuesday morning to protest alleged staffing shortages.
Now Amazon and shipping company DHL Worldwide Express, which are both customers of ABX, will have to pay the price.
ABX operates 35 flights daily for Amazon and 45 flights a day for DHL, according to Teamsters Local 1224, the union representing the pilots.
This could cause major disruptions and delays for some Amazon customers during the busy holiday season, according to the union.
The pilots say they are striking because they have been forced to work "emergency assignments" during contractually obligated time off as a result of alleged understaffing.
So far this year, pilots have been scheduled to cover more than 8,000 emergency assignment days on days they should have had off, according to the union.
Amazon and ABX Air did not immediately respond to a request for comment.
The striking pilots are picketing on Tuesday outside of ABX Air's headquarters in Wilmington, North Carolina and outside DHL's North American hub at Cincinnati/Northern Kentucky International Airport.
Pilots at ABX Air and four other cargo carriers that fly for DHL voted to strike earlier this year if negotiations with the company stalled.
Disclosure: Jeff Bezos is an investor in Business Insider through his personal investment company Bezos Expeditions.