The International Brotherhood of Teamsters said FedEx Corp. intends to “blackmail Congress” by threatening to cancel a multi-billion dollar airplane contract order if its FedEx Express workers are allowed an easier path to unionization.

The Memphis-based carrier noted in its third quarter filing the with SEC that in January it exercised its option to purchase 15 additional Boeing Corp. B777F aircraft and got an option to purchase 15 more.

Congress is now considering a bill that would change FedEx’s regulatory oversight from the Railway Labor Act to the more union-friendly National Labor Relations Act.

“The bill should be evaluated on its merit, not upon the threat of FedEx to fire another torpedo through the American economy," Teamsters International vice president and director of the package division, Ken Hall, said in a statement. “It is a slap in the face to Congress and the American people.”

The statement says all FedEx Express workers are covered by the Railway Labor Act whether or not their duties are directly linked to the air fleet. This includes delivery drivers, sorters and truck mechanics.

The National Labor Relations Act would allow those non-fleet-associated workers to unionize by individual terminals. The NRLA would require union votes from every worker at FedEx Express.

“Fred Smith should be treating workers like a crucial part of a successful business, not like a bargaining chip in his political games," Teamsters general president Jim Hoffa said in a statement.