How can i keep my kids calm on the plane?

I'm moving in about a week across the country and i have a 1 1/2 year old and an 8 month old. They are well behaved sometimes but they're typical kids who misbehave at the wrong times. They're both going on the plane with me and it's just going to be me and the two little ones. My 8 month old is going to ba a lap child on my lap and my 1 1/2 year old will have her own seat. I already have a double stroller for the airport. But the problem is that it's a long flight and I do not want them to start throwing a fit on the plane while everyone is trying to relax. So does anybody have any advice at all about how to keep them calm or what to do with them so they can behave themselves?