The first half of this post was written a little over 2 yrs ago while packing for my first solo flight with 2 of my daughters (I now have a 3rd baby girl!). The 2nd half was written the day after our flight to share how things went.
Packing & planning ahead-
Since A (2.5 yrs old) has her own seat (since she's over 2 now) we can carry on 2 "personal bags" for free (check your airline's website for bag rules as many are getting more strict about number/size of carry-ons). The above diaper-backpack was my splurge last spring. It's a little big for everyday use but perfect for traveling with what seems like twins sometimes. My purple diaper bag/tote was a special birthday gift from my mama when I was pregnant with C. I've carried it everywhere (with & without the girls & it's nice to have a diaper bag that doesn't look like a diaper bag so I don't have to switch bags when going somewhere without the girls). I'm flying with it because it holds a lot & I can easily hang it from our umbrella stroller (that A will ride in), while carrying the backpack on my back & C (14 months old) on my front in the baby carrier.
Below is what is packed in the diaper bag/tote. I tried to put things that I will need quick access to when going through the airport. (It is hard to reach a backpack when you have 2 babies to keep track of).
Girls' jackets, A's blanket, snacks, new toys!, wallet, tablet, copies of girls' birth certificates (I've never needed these when flying but better safe than sorry), C's cow
Baby food can go through security & does NOT have to be in the same zip lock as your other carry-on liquids. TSA may do a quick test on them.
Everything in the backpack-
Wipes, changing pad (came with the backpack!), receiving cloth (changing pads are tiny), 6 diapers (total for 2 girls), plastic shopping bag for trash/dirty clothes, dirty diaper trash bags, baby powder (helps with smells- I pour some into filled dirty clothes/dirty diaper bags), change of clothes for each girl.
C's blanket, 1 empty bottle, formula (C is not fully on cow's milk yet), toddler cookies, sanitizing cleaning wipes (airplanes are dirty!), spit cloth.
Once through security, I will buy bottled water to make C's bottles. I will also buy A a small milk (with straw!) for the flight. (Baby/toddler ears do better with the change in pressure at take-off/landing if you provide a bottle/drink with straw to suck on.)
Dollar bin flash cards, princess light (C will push a button over & over & over), dollar bin notepad with crayons, new books, finger puppets
This is my first flight alone with babies so I want to make sure I have more than enough NEW distractions for the flight so that I feel CONFIDENT that I can contain them both for 2 hours. Another new book with stickers is in our checked bag so there will be something new on our flight home as well.
A few Mama items-
Brush & hair clip, oil blotters (traveling = greasy forehead for me), deodorant, gum, chapstick, tablet/phone charger, ear buds
I will also pack an extra shirt for myself. Who knows what will end up on me!
UPDATE after my first solo flight with my 2 toddlers-
A kind TSA agent helped us through security by dealing with my stroller for me & bringing me my bags once they had tested my hands. (If you wear your baby, you do not have to take her out of the baby carrier to go through security. You simply walk through the metal detectors while wearing her & then they do a seconds long test of a little cloth they wipe your hands with.)
Security lines were long so I ran out of time to find A milk but her ears did fine with just a smoothie pouch to suck on.
We boarded AFTER "those with small children" & we had more than enough time to get situated when we did board & less time on the plane = better for babies & mama.
Things I am glad I didn't leave at home:
Extra shirt for me! (Wearing C left fuzz from her new shirt stuck to my white shirt)
New toys! (Especially princess lights, toy phone & board book with flaps)
Toddler cookies! (We rarely have these at home so they were a nice, distracting treat)
Both girls did great. I expected C to nap & she didn't; however, we managed exhaustion tears with some cartoons & apps on my phone. I did let both girls stand in our row (on the floor) for about 5 mins to stretch their legs but that may have just made sitting back down more confining to them.
When flying with babies, remind yourself that a flight is not never ending & many people have children in their lives & so they understand what you're up against in that plane & daily.
Also- baby/toddler tears are perfectly normal.