I just flew from Chicago to New York at about 6 weeks. The doctor said it would be fine, and it was. Just keep hydrated, go to the bathroom when you need to, and make sure you get up and move around every hour or so.
On the plus side, being pregnant made me tired enough that I actually managed to nap on the plane.
ME 28 - PCOS, some male factor
2 failed IUI
4 rounds of clomid, all BFN
07/07 - Started first round IVF - Cancelled
08/16/07 - Started Lupron
08/24/07 - Start stims (Menopur)