Hey I know this forum is probably dead, but I'm a little confused. I hit the air units (helicopters) in the first mission on Bratt's campaign. None of my units are AA. How do I deal with these?

You will have to get the right technology and then build some Pluton units. Station these around your military HQ. The Alligator ship can also attack them.

Neither are very good at shooting them down, you will need to attack several times.