I personally believe that all members of congress should fly coach, no matter what circumstance, as even members of the public that are old or have disabilities still typically do not get to experience first class, so that they are consistently empathize with lives of "the people." However, I do not members of congress should be forced to fly coach. If they would like to fly first class on their own dime, that is their prerogative. I would hope that their constituents have a mechanism to notice that and then vote accordingly next election. Costs should not be a significant part of this discussion though, as each congressional office receives a travel budget and if they don't spend it on first-class, they'll find something else to spend the saved money on. If cost is really a concern, then maybe we should provide incentives for congressional offices that spend the least amount of their travel budget.