My son works for Fedex Express. He been there for 4wks and has not received a paycheck. He told his manager with no luck. What can be done?

My son works for Fedex Express. He been there for 4wks and has not received a paycheck. He told his manager with no luck. What can be done? He was told each week it should be there the following week and each time it comes, there is no luck. He work at the Philadelphia Airport Fedex. He started to seek out his own help my contacting his manager's boss and even payroll and HR manager. Still no success. Everyone is saying to him to be patient and that they are doing all that can be done. Is this normal or ok? My son still continues to go to work each day as scheduled and on time. Most recently his manager's came down on him about the course of actions he has taken by contacting corporate and the vice President of the Philadelphia division in regards to the issue. The manager's said to him "I know you called the Vice President. I can lose my job. Still you have no check" , are just the few things said to my son about his ability to resolve the matter. What if anything can be done?