Ice packs! Which is a bit trickier when you're flying, what with the ban on liquids in the cabin, but it's quite possible to take it - I travel with Humira all the time. So what I do is take a little cool bag to fit my Humira pens in and start with no ice or ice packs except for the frozen meal that I take for the plane.
I don't really eat plane food and like to know that I'll have something 'safe' with me that will keep me as healthy as possible on the journey. But it also does double duty as an ice pack that I'm allowed to take with me on the plane! I've never had a problem and don't imagine anyone would unless there was a high liquid content to the food...so basically not soup!
Then when that frozen meal ice pack has either defrosted or I've eaten it and I'm on the plane, I ask the flight attendants for ice and put it in a ziploc bag in the cool bag.
And then if I have a connecting flight and have to go through security again I have to remember to throw out that ice before I get to security and repeat the procedure once I'm the other side.
You don't need to worry about the Humira being at room temperature for a short time - it still works when it's been at room temperature for up to 8 hours so if you keep the time much less than that it's fine.
And I've never had anyone question me about the syringes/pens going through the x-ray machine either. Sometimes I explain in advance and they're not in the least bothered. It's a tiny quantity of liquid and I think they get a lot of people travelling with similar things. The first time I travelled with them I was nervous so I got a letter from the pharmacist who delivers my Humira stating what it was and why I carry it but I've never needed it.
Edit: I just read in the Humira thread that they now say it can be out of the fridge for 14 days. I don't know if I can adjust to that idea lol but I guess it makes travelling a lot easier. If anyone still prefers to keep it refrigerated because that's what we're used to now, the above tips still work