Jessy, most airlines let you fly up to 30 weeks but my midwife has told me that it would be a good idea to take a document signed by your doc/midwife/gyne stating how many weeks pregnant you are and that you have no known complications, just in case anyone on the plane or at the airport decides to kick up a fuss.
She also said that flying poses no risk for the mum or the baby at all. The only risk is that you´ll go into labour up above the clouds which is why they don´t let us fly later on in pregnancy.