Thought we'd post about our experience traveling by air with a 6 month old baby, for anyone looking for information on the topic. We asked for and received a lot of really helpful advice before we went.
For background: we had two flights each direction. The first was a four hour flight across the country, the second a shorter flight, but crossing the border into the States. Our holiday was ten days long and we explored beautiful Cape Cod and Boston both by car and on foot.
Booking the flight: B phoned to book our tickets because you can't book infant flights online. Even though it's technically "free" for babies under two, it costs twelve dollars so that they have a "ticket" of their own...apparently so Homeland Security can keep track of who is coming into the country. The Air Canada agent very kindly booked us seats so that if there was a possibility of having a section of three seats, we would have the two outside seats and potentially an empty one between us for her to lay and wiggle on while we were in the air. This ended up working only for our one flight across Canada, but let me tell you, it was so worth it to be able to lay E out. She could move around freely and play with her toys and it gave us a break from holding her as well.
Pedestrian-style: We have our own style of packing and moving when traveling--we don't like rolling luggage. Because we tend to do a lot of walking when we travel, we like to utilize our big big hiking backpacks instead, so that we're always able to get places on foot easily. Consequently, we decided that for our ten day trip, we'd pack one big backpack, one smaller one, and one diaper bag. Then, when we were all loaded up, I would carry E in a sling. So picture B with a big backpack on his back, a smaller one on his front, and me with the diaper bag on my back and a little girl on my front. This worked surprisingly well, though it was a lot of weight on our shoulders.
Security and customs: we were worried about how this would go since we'd have a potentially grumpy little person who might also be carrying scissors or fingernail clippers in her pockets that we'd have to answer for (you never know ;) ). But everyone was incredibly patient with us as we made our way through--including the security people and the customs and Homeland Security people as we crossed the border. It helped that E smiled at and made friends with everyone. :D
Airplane specifics: It was worth getting on the plane during the early boarding call. Because we had a baby and not an active toddler who might have benefited from getting on last, we took the opportunity to get on first. That allowed us to get on and find our seats, pull out toys/receiving blanket/changing paraphernalia and have it all organized and ready for quick access.
The attendants wanted me to hold E in an upright position as we took off and landed, but I found the best way to keep her calm and enable her to adjust to the air pressure changes was to breastfeed as much as possible. It ended up working really well--she'd settle down and feed and would fall asleep and not even notice that we'd left the ground. I'm pretty comfortable with nursing in public, and I think this helped E to be really comfortable and relaxed too.We also encouraged her to chew on her toys lots so that her jaw worked. We are non-soother non-bottle parents, which determined how we handled this situation.
We rented a car seat from the car rental place rather than bring our own, again so that we didn't have that extra item to haul around.
Further on the sling, our first flight was very early in the morning and our little girl likes to sleep in. So upon our arrival at the airport at four in the morning, I tucked E down hammock-style in the sling and she fell sound asleep, warm and secure against me. She could have been screaming mad to be up and surrounded by strangers, but she was not.
Extra items: a friend advised me to bring 1) a heavier blanket and 2) toys E had not seen before. These both turned out to be helpful things indeed. The blanket came in handy during the time after security and before we boarded, and during layovers, because we could lay E out on it and she could freely play and wiggle and we didn't worry about germs and dirt on the floor. The new (to E) toys were a great distraction for E when she was getting bored or tired, because she'd never seen them before.
Also, we dressed E in soft waistband-less clothing for the flight (ie a sleeper) so that there was nothing constricting and annoying her. This also made it easy to strip her down for diaper changes, and to delayer her when the plane suddenly got really warm.
I was pretty worried about how it was going to go, traveling internationally, over eight hours and two planes and surrounded by strangers and totally new circumstances, but E took it completely all in stride. She was a joy to travel with and we'd have it no other way. So, I hope this information can help someone else!