M.M.
I had the same pump. I just gave the baby to my boyfriend and went into the bathroom, but the cover thing down on the toilet and pumped. The first trip, I informed the flight attendants that I would be in there pumping--they were SO GREAT about it--they told everyone who walked up to not bother waiting and to go to the back of the plane. I think they have seen it a lot so should be helpful--I would suggest trying to sit closer to the back or middle of the plane so you can go to where there are two bathrooms (usually in the back). That way you aren't making people mad by being in there for so long. And remember: you are doing something GREAT for your child--if people get annoyed--LET 'EM! Just ignore it. Oh--and pumping in the bathroom will eliminate the noise issue.
The suggestion about the hand pump is good too: one came with my Pump In Sytle: it works pretty well, and gives you a great little workout for your arms!! It is VERY compact and doesn't require a whole extra bag--since the flight is only 4.5 hours, you only have to use it once or maybe twice.