On page 124 under Reserves, it states half your units rounded up must begin the game on the table. Units that must deploy from reserve are ignored for the purposes of determining how many units may remain in reserves. So every one of your flyers as well as any other reserves-only units may start in reserves, and up to half of what's left may be embarked on those flyers or otherwise kept in reserves.
Ninja'd by scscofield. I believe he's thinking of the old Dawn of War deployment scenario.
"Trying to make some sense of it all,
When I can see it makes no sense at all"
"Fools to the left of me,
Jokers to the right,
Here I am,
Stuck in the middle with you."