USERRA protects your employment rights/seniority. Won't protect your right to J/S on other airlines as that isn't within FedEx's power.
Will protect your seniority/pension/etc.
For Example, healthcare is a protected benefit, but, the company is not required to pay for it. The company is encouraged to continue paying the employer portion for your healthcare, but isn't required to. Company can make you pay up to 102% of the premium....and that's the full premium, not just the portion of it "we" pay every month