How does your toddler sleep on the plane?

We are flying to Italy and then to Israel next week We aren't bringing Alex's car seat because we don't need it.

The last time we flew to Israel, while Alex fell asleep, I couldn't sleep at all because I had to watch her to make sure she didn't roll off the seat and onto the floor on the airplane.

Is there anything else I can do in anticipation of our red-eye flight to help her be a little more comfortable falling asleep on the plane? Any suggestions?