I am flying in two weeks (at 31w). Airlines (or at least mine) are fine with you flying up 'til the last month. Also, my doctor and I have discussed the trip and she is okay with it - again, the real concern for them is after 35 weeks or so. This is the 3rd air travel trip I've taken since my BFP. If you go, drink LOTS of water on the plane, get an aisle seat, and pack tons of snacks.
That said, if it makes you uncomfortable, by all means, beg off. You can use the pregnancy as an excuse not to go.