For me, I have to dress up if I want to Non-Rev in first class. When ever I fly I dress up, even if it is on an express flight because, I may have to get creative. United's Employee/Dependent Dress code is as follows:
HIGHLIGHTS OF ACCEPTABLE ATTIRE:
IN COACH: Jeans, Denim clothing, athlectic/tennis shoes;dress sandles, loose fitting knee length Bermuda Shorts on all flights within the United States, Canada, Puerto Rico, and Mexico.
UNACCEPTABLE ATTIRE IN ANY CLASS:
Any clothing that is torn, frayed, has patches or holes, sweat clothing. T-Shirts, bare feet, bathing suites, beach sandles, bare midriffs, extreme mini skirts, halter or bra tops, sheer or see through clothing, tank tops, sleeveless muscle shirts, and undergarments worn as outer garments
UNACCEPTABLE ATTIRE IN FIRST/BUSINESS CLASS:
All of the above items plus, jeans, denim cloathing, athlectic shoes, hiking/military style boots, shorts, baseball caps, lack of hosiery or socks, skin tight pants execpt when worn with a mid-thigh length top.
CUSTOMER SERVICE REPRESENTATIVES HAS FINAL SAY WHEN IT COMES TO THE DRESS CODE!!
Hope that helps!
Once again that is the pass travel dress code for United Airlines.