All Russell said was:
"I can fly, I'm a pilot"
It was later in the briefing that Russell filled in a bit of his story,
(Russell giving his background to Major Mitchell) Well, I'm, uh, Russell Casse, sir. And, uh... after 'Nam, I got into crop-dusting. And, uh... been doing that ever since. On a personal note, sir, I'd just like to add that, uh...ever since I was kidnapped by aliens 10 years ago,...I have been dyin' for some payback, and I...just want you to know that, uh... I won't let you down.
But in an alternate ending Russell flew his biplane into the alien ship...
[Narrator] So this scene exists in the movie as is but it ends a certain point. We wanted show that they were so desperate for pilots that they'd ask anybody. That's where we ended in the final version of the movie, but here's how it originally ended...
[Major Mitchell] Sorry, sir.
[Russell Casse] Wait a minute you don't understand... I... I got to be a part of this, it's important to me. These guys, they, they, ruined my life.
[MM] Why don't you just go sleep that off sir.
[RC] scoffs But I can fly! You want people that can fly, I can fly! It's the one thing I do...
[Narrator] The original idea was to show how he was... the one talent he had he couldn't use in an important moment. He would later show up in his biplane and save the day. But what we lost by that, we never able to actually see him sobering up, we weren't able to see him in training, and so all those scenes were shot later in the last minute.
So what this tells us is that Russell originally wasn't supposed to have any jet-fighter experience, but was later changed to fit the story better.