[My Sophia]

i don't think any airlines actually require a health certificate for domestic flights any more. check your specific airline's website. it will have info on their requirements for pets. when you go through security you'll have to take your baby out of the carrier and carry her through the scanner. probably will have to take the collar/harness and lead off because of the buckles, depends on how sensitive they've got the scanner set. they'll tell you whether you need to or not. make sure there's a blanket in the carrier as the floor of the plane will be cold. you won't be able to take water through security so it might not hurt to stick a couple of bottles of water from home in your checked luggage. changing water can sometimes cause upset stomach or cause them to not want to drink as much as they should. throw in a little emergency kit with nutrical, hydrogen peroxide and benadryl also.

eta: Doesn't hurt to have her shot record with you also, whether you're driving or flying.