Its not against the rules, in fact military members are authorized to use their miles earned on govt travel to upgrade. I can tell you that it would make a young sailor/airman/marine's day if you upgraded them, they're not likely to fly first class often on their $18,000 a year salary and they really are doing a lot for their country without much recognition. Someone bought my helo crew breakfast two weeks ago at a local airport where we had stopped after an all night search and rescue case and I can tell you we are all still talking about it!