There is a guy, Mithridates the Great, ruler of the Pontic empire, who was one of Rome's great adversaries. He was famous for, among other things, realizing if you take a little bit of poison every day you can build up your resistance to said poison. A rather useful insight as regicide in that area was done mostly via poisoning. At parties, he would chug a goblet with enough poison to take out the entire room as a party trick.
....I'm pretty sure drinking airplane coffee is the same thing for us. Between that and somehow every single deadhead sitting next to that one guy who is blowing his nose and coughing, we should be invulnerable.
(Anecdotally, "The Poison King" about his life reads like a GOT season (pre season 6) and totally worth the read.)