Strictly speaking, FedEx is regulated as an airline (under the Railway Labor Act). FedEx workers aren’t legally prevented from forming a union but it is harder

Strictly speaking, FedEx is regulated as an airline (under the Railway Labor Act). FedEx workers aren’t legally prevented from forming a union but it is harder for them to strike under certain circumstances. I believe DHL is also regulated as a airline and was more unionized when they were still in the domestic delivery business in the US.