I am an introvert and I enjoy talking to people on the plane. If they're boring, I put my headphones on and read my book. (If the other person has a book, notice how they interact with it. Wait about thirty seconds- if they're still holding their place with their finger / clearly not disengaging with it, put the conversational ball in their court, and see if they keep talking to you or go back to reading.)

I also recommend introducing yourself as soon as you sit down. They're unlikely to be deep in thought, and it can be awkward to do without a clear opening if you didn't do it immediately. I wasted about half an hour of a flight with a cute guy because I didn't do it on sitting down, and then didn't want to interrupt Skymall. (Thankfully, him finishing reading it was an opening, and then we talked for the remainder of the flight.)