Anyway, long story short, traveling with an 11-month-old took a lot of planning and multiple Amazon purchases! Here's what worked well for us:
If your child is over 2 years old, you have to buy them their own seat on the plane, so this won't apply; however, if your child is under 2 years old (bring a birth certificate to prove it, just in case! I've heard Southwest asks 100% of the time), you have the option to travel with them as a "lap child". (You can also buy them their own seat, but it's not required and it's at the full adult fare). Make sure that, when you're booking your tickets, you book a lap child on your ticket if you're going that route. Some airlines don't allow you to do this on their website so you'll have to call and add the baby to your reservation after (American is this way). It is important for the baby to be noted on your ticket as a lap child because there can only be 1 lap child on each side of the aircraft due to the number of oxygen masks. Double check at the airport that your boarding pass prints with "infant" or "lap child" or something similar written on it.
Check your airline's website for their policies on traveling with infants. Most airlines allows you a generous allowance for baby items, even if your child is flying as a lap child (i.e., doesn't have their own ticketed seat). American Airlines allows you to bring a stroller, a car seat, and a diaper bag IN ADDITION to your normal carry-on allowance (you can either check these items for free at the ticket counter or carry them to the gate). I printed the airline's policy on all of this in case anyone tried to give us any trouble, but no one even blinked.
You'll also want to plan ahead how you want to get all of this stuff on the plane. One option is to check it at the ticket counter (since it's free); however, they manhandle that stuff and I didn't want our stroller or our carseat being damaged....ESPECIALLY the carseat, since 1) it may not work effectively in a crash if it's been damaged, even if the damage is not visible, and 2) if it gets damaged and/or lost in transit, you're stuck at the airport without a way to leave....so you'd have to wait there while someone made a Walmart run for a carseat.
Anyway, we decided to gate check our car seat and stroller, which just means that you take it up to the gate agent at the gate, they'll put a baggage tag on it (and give you a claim ticket), and you'll drop it off on the jet bridge when you board the plane. They'll put it with the other checked bags (but there is less time / less distance for it to get manhandled) and it will be returned to the gate (not baggage claim) when you arrive at your destination. If you do this, you'll want to protect the stroller and car seat from damage / dirt / rain -- see below for the bags we bought for this purpose.
I'd also recommend packing as light as possible. We packed C's stuff in with our suitcases to minimize the number of bags we had to take.
We ended up taking 2 carry-on rolling suitcases, a tote, a backpack, the carseat, and the stroller (so 6 total items). The tote went on top of 1 rolling suitcase, the carseat was strapped to the other rolling suitcase, one of us wore the backpack, and the other carried the stroller (it had a shoulder carry strap).
For getting through security and around the airport, it was easiest to wear C in the Ergobaby carrier. You do not have to take your child out of the carrier to go through security; they'll let you walk through the metal detector (not the body scanner thing) wearing the baby and then they'll swipe your hands (to test for explosives, presumably?). Easy peasy. It was easiest for me to go first, with C, so I could collect all of our stuff from the x-ray conveyor as Blair sent it through.
As for the baggage, everything except the carseat will go through the x-ray conveyor like normal (the car seat will not fit). They'll take the carseat through the walk-through metal detector and then give it a visual inspection (so you do have to unstrap it from the rolling suitcase or take it out of whatever bag you might be carrying it in). We re-hooked it to the rolling suitcase immediately after security to wheel it to our gate.
If your airline allows pre-boarding for families with small children, do it! It is so much easier to board the plane without feeling rushed/stressed from the line of people behind you while you're trying to get situated. We dropped the carseat and stroller on the jetbridge and I wore C in the Ergobaby carrier until we got to our seats.
Our flight was relatively short (~2 hours); during boarding and the drink service, C was entertained to watch the people walking down the aisle. He also enjoyed playing with the magazines/brochures in the seatback pocket for a short time. However, during the majority of the flight, there wasn't much to see (and he is not one to nap in our arms), so we had to keep him occupied. He has never watched TV or the iPad, so we didn't want to bank on that working, so we went to the foolproof option: snacks. Yes, C basically snacked the ENTIRE duration of the flight. To keep our seats cleaner, and to make the snacks last longer, we handed him 1 piece at a time (otherwise, he grabs food by the handful and shoves it in his mouth, while dropping half of it). I had packed his lunch in a small cooler (diced vegetables, deli turkey, mozzarella cheese, etc.), so we did that first....then resorted to Cheerios 1 at a time...and finally a pouch. We've never given him pouch baby food before but it was convenient, it was mess-free, and it required him to suck/swallow, so that helped keep his ears from popping (I nursed during takeoff and landing, but this helped during the descent).
Here are the things that were must-haves for us for the trip (especially the flight):
1. Travel carseat
Since we were going to be renting a car at our destination (Denver) and driving to Vail, we needed a carseat. (Note: if you're still using an infant carseat, you can just bring that. This is for a convertible carseat since C is too tall for the infant seat).
I had read enough horror stories online about trying to rent carseats through the rental car companies to know that we didn't want to go that route. To summarize: even if you reserve one, they're not guaranteed to have them (or the right kind - e.g., infant, convertible, or booster) when you show up; they may be dirty; they may have damage that isn't visible (since you don't know the history); you won't have the manual or experience installing it; and the cost to rent ($5-10/day) adds up fast. I also knew that we didn't want to bring our everyday carseats (Britax Boulevard ClickTights); although they are super easy to install, they are HEAVY AS ALL GET OUT (25+ pounds) and I did not want to lug those through the airport. Plus, they were expensive, so if they got damaged by the baggage handlers, I didn't want to shell out $350 for a new one.
After doing some research, we ended up buying an Evenflo SureRide DLX, which was $99 at Babies R Us (so ~$80 after a 20% coupon). It only weighs about 10 pounds, was easy to install, and is relatively compact so it fits in most vehicles (which was important since you never know exactly what rental vehicle they'll give you). It fits rear-facing to 40 lbs and forward-facing to 65 lbs. (A cheaper option is the Evenflo Tribute ($60 before coupon), but it only goes to 40 lbs rear and forward-facing, so it wouldn't last us as long and we'd end up having to buy another travel carseat in a couple years). Anyway, the Evenflo Sureride ended up working out great and would be a great, budget-friendly option for a 2nd carseat for a spouse's or grandparent's car.
2. Traveling Toddler Car Seat Accessory
The Traveling Toddler Car Seat Accessory is a a strap which hooks up to a carseat's latch connectors and allows you to strap the carseat to a normal carry-on size rolling suitcase. We didn't try it, but they say that you can even strap your child into the carseat while you're wheeling it around the airport (it was definitely very secure on the suitcase). We used this to wheel the carseat to security and around the airport, right until it was time to board the plane.
3. Car Seat Gate Check Bag
This seems redundant of the strap, and, in theory, you could go without the strap mentioned above and use this bag the whole time. I read a million reviews on Amazon and this one was supposed to be more durable than the J Childress brand (plus has a lifetime guarantee). It has a shoulder strap, which is nice, although only if your carseat is as light as ours was (I can't imagine trying to carry our 25 lb Britax seat in this bag). They make more expensive backpack-style carseat bags but this one worked fine for our purposes so I'm glad I didn't get the more expensive, brand-specific bag. We put the carseat in this bag after we got to the gate (we kept it strapped to the suitcase the whole time we were walking around the airport because that meant it was one less bag to carry/keep track of).
4. Umbrella Stroller
Unless you have a really good reason, I wouldn't bring a big or nice stroller, like a jogging stroller; most airlines will require you to check it at the ticket counter and can't guarantee that it won't get damaged in transit. If you bring an umbrella stroller, you can take it to the gate and, if it's small enough, maybe even on the plane (we gate checked ours). We have a Summer Infant DLite umbrella stroller which is lightweight, easy to use, and has a sun canopy. I haven't tried out any other umbrella strollers, and a friend gave us this one, so I haven't really researched other options to know how this one compares.
5. Stroller Gate Check Bag
Since umbrella strollers are kind of flimsy, you'll probably want it in a bag when you gate check it to keep it clean, dry, and less likely to get caught on something and broken. This Angel Baby bag (same brand as the carseat bag) worked great; it doesn't have a shoulder strap, while the stroller itself does, so we carried the stroller through the airport (not in the bag) and put it in the bag when we got to our gate.
6. Ergobaby Carrier
As mentioned above, it was super convenient to carry C in the Erbobaby carrier through security and throughout the airport, up until the point I sat down in my seat on the airplane. Then, we just stuffed it in one of our carry-on bags. (As a side note, we also hiked with C in the Ergobaby using the back carry and it worked out great! He snoozed the whole hike with the sleeping hood on to support his head from flopping). I can't get over how comfortable it is to carry my heavy (20+lb) baby in this carrier; it really does support his body weight on my hips, rather than my shoulders/back, such that I carried him all around the airport AND several hours hiking without any discomfort.
7. Sippy Cup
C's sippy cup was easy to fill up at water fountains in the airport or from the flight attendants on the plane and provided both hydration and an activity to occupy him :) We like the Playtex Training Time Straw Cups.
8. Small cooler + all of the snacks
Snacking was C's main entertainment on the flight. Think about how many snacks you think you need, then double or triple it, just to be safe (remember the 9 hours we got stuck in the airport?!) I used a small cooler (2-bottle size) and brought a few Tupperware containers with chopped up mozzarella cheese, turkey, and steamed vegetables, the ever-present Puffs and Cheerios, and several pouches of baby food (even if your kiddo is mostly past the baby food stage, these are great for travel since they are not messy and do not require refrigeration!) If you're bottle-feeding, you'd want to bring bottles and breastmilk/formula, too.
9. Antibacterial wipes
I found packages of antibacterial Wet Ones in the travel size section at Target, and they were great for wiping down hands, armrests, airplane tray tables, high chairs, etc.
10. Stick-on disposable placemats
I do not leave the house without these Table Topper disposable placemats, and they were great on the trip as well! They stick securely to a tabletop with 4 peel-off adhesive strips, making it easy for a little one to eat a meal in a restaurant (without having a plate to fling across the floor). I like to wrap the bottom edge of mine under the table so C can't put his hands all over the grimy underside of the table.
11. Pocket bib
These Baby Hiccups pocket bibs are a lifesaver; we use them for every single meal at home, and it was great having one on the trip as well! The pocket on these catches pretty much every bite that falls out of C's mouth, saving us from having to pick up food from the plane/restaurant floor. I also love that the material is easily wipe-able with a baby wipe for easy cleanup while traveling.
12. Nursing cover
Nursing during takeoff and landing, like everyone suggests, seemed to prevent C from having any ear pain from the change in pressure. I love the 360-degree-coverage of the Covered Goods nursing covers for discreet nursing in public, whether on a plane, in a mall, at a restaurant. etc.
13. Changing pad, diapers, wipes
I love this JJ Cole travel changing pad with a pocket for a wipes case and diapers. Bring way, way more diapers and wipes than you think you'll need - you never know when your flight will get delayed and all of a sudden you're spending 9 hours in DFW airport (not that I know from experience....) If there is ever a time NOT to be caught short on diapers or wipes, it is while traveling! You can buy more when you arrive at your destination for the remainder of the trip, but do not skimp for the travel days!
Bring a few small toys/books for entertainment. I didn't find that these entertained C for very long, so I'm glad I didn't use much room for packing toys and books. He was more entertained by snacking, people-watching, looking out the plane window, playing with the magazines in the seatback pocket, and more snacking. Some people bring an iPad with games/shows/movies loaded on it, but we chose not to; C doesn't watch TV or movies at home, so it's not something he's used to and it doesn't hold his attention span.
15. Pacifier with clip
A pacifier helps with ear pressure (and keeps your plane neighbors happy), and a clip is a must to keep it from getting lost or dropped on the gross airport/plane floor.
More than anything, tell yourself that you'll never see any of these people again :)