I thought I'd post a couple pictures about what I typically do to indicate flying monsters.
I use these little plastic champagne glasses I bought at Hobby Lobby. You get 24 for $6 and Hobby Lobby ALWAYS has a 40% off coupon on one item, so that makes them $0.15 each!
|With a little blue sticky tac, you can make the cups "double decker"|
You can use them cup up or base up, whichever you like better. If you use them cup up, you can easily put some small dice inside the cup to help indicate altitude.