I have pumped all over God's green earth i.e. airport, car, airplane bathroom, Mardi Gras parade, etc.
Bring your electric pump. You will need to get the battery adapter. I have the Medela pump in style and it came with one.
At the airport, ask an attendant or janitor where a family restroom is. If they are ignorant (which a lot of times people are when it comes to breast pumping), go in a stall at the airport and set up shop. None of the restrooms have an electrical outlet.
Depending upon how long your flight is and whether or not you are on a plane with more than two bathrooms, you could pump. I generally will pump on a plane that has two bathrooms in the rear of the plane and let the flight attendant know that I will be occupying that bathroom for about 20 minutes.
Once you get to where you are going, pump in the car. I have a hands free bra. I will set up and put my nursing cover on and drive to wherever I am headed. If you are not comfortable pumping and driving, find a parking lot. Do not forget to bring your nursing cover.
One thing that helps is try not to stay on a every 3 hour schedule like you might normally do, just pump wherever you can even if you just pumped an hour ago.
FYI: I did recently buy a Medela mini electric. It is about $70. I bought it because I have found that with two kids and life I do not always have time to sit and pump. I have used it several times at the airport and I do it every morning on my way to work for about 10 minutes on each side. It is not the best but it does the job to relieve myself.