"28% off on any published fare within North American market."

That's United's standard discount for large corps for business travel. Three companies (all household names) have paid for my travel with the same 28% discount on United. In fact one of them, much to my dismay, insisted on booking me to a UA/AC codeshare instead of on AC in order to get the discount.

Two of those three corps do not allow personal travel at the discounted rate due to contractual obligations with United. One of those three corps does allow employees to avail of the discounts for leisure travel if booked through their travel dept. - I don't know if that corp has a different contract or they are just ignoring their contractual terms with United.

I can't be more specific as corporate contracts with United are covered with an NDA. All I can say is the amount of discount (28%) and the terms of discount (down to the exact text printed on the ticket with just the company name changed), were identical for all three of the large corps I've ever dealt with. So after going 3/3 this leads me to generalize that most of UA's corporate contracts are the same as well. BTW, Continental provides a variable discount that's around 30-35% depending on the volume of travel.