"If travelling on an Economy Class ticket ID passengers must also be well-groomed, neat and clean in appearance. Please remember that whilst ID passengers may wear clean and tidy denim jeans (i.e. not torn or frayed), they will not be upgraded unless they are able to change into more formal attire. ID passengers will not be accepted for travel in Business or First Class if wearing denim jeans."

You won't get an upgrade anyways, jeans OK