There's only one way to find out. Like most of us, you're going to find it more difficult than those who don't stutter, but surely that's more reason to give it a shot. It's not like commentating a sport or something like that where I'm sure no employer would give people like us a chance. Sure, speaking is important, but there are more facets to being a flight attendant than just being able to speak. You should also consider the fact that you'll be asked the same questions most of the time and if you can answer those relatively fluently, you should be fine. I find with my job as an English teacher here in Japan, I rarely ever stutter (I do quite a bit in real life though) because I'm using the same phrases etc over and over again to the point where it's almost a script. It's when I'm talking freely that the stutter tends to rear its ugly head, but it's never that bad.