We're flying Southwest. Will our Britax Roundabout fit into the seat on the plane? Also, do you strap the carseat in yourself, or do the flight attendants do it? Do you only use the lap belt, or do you tether is too? I haven't flown in years, I have no idea if they even have a place to secure a tether on planes!?! Do they still have the families with little ones preboard so we have time to get the carseat installed? Any other tips are appreciated! This is our first time flying with our 3 boys. I'm getting a wee bit anxious! LOL 
