Choose you favourite air bocker
under 1 million
Basic Shield Of Flight
Double Dryer
Earthen Scorchstone
Mystical White Cloak
Psellias Blessing
Scarab Medallion
Shiny Shoal Shell Shield
Sinsis Crown
Warriors Rectangular Shield
Winged Scarab
The poll is not important. I like to read opinions
Things to consider :
You're not going to face air icons only.
Price .
Usefulness

.
It's a shame the best choice isn't on your list, a pteri pet.
Considering the majority of them are strictly defensive shields, I'm assuming the defense for the pet in question is reasonably trained. With that being the case, the only two that jump out at me are the
Earthen Scorchstone and the
Winged Scarab. The Scorchy is the better "air" defender between the two, but the Scarab is basically a full physical blocker. Physical is attached to practically all weapons nowadays, and the air icons it blocks (and deals) are a nice little bonus. The Scorchy is more of a situational defender, and could often be a dead spot in your set, the Scarab will never be.
I'd take the Scarab.
I'd personally use a Pteri, like dbml has said. 40% resistance is HUGE.
I actually like using Earthen Scorchstone, but since I don't train DEF, the Winged Scarab is the best choice for me because it has physical defence that leads to dmg = DEF boost times 2 (Go 55 boost for 3 dmg!).
I voted for Double Dryer because I like reflectors, but I'd also probably go with a pteri. 40% resistance is crazy good.
I was beaten to my first thought of pteri as well.
Voted for earthen scorchstone cause well it's cool

and i don't prefer reflectors.
None of them. Aside from morphing Pteri, there isn't really a good route to defend Air for less than a million (on the plus side, there's not really much that can deal Air, either).
Double Dryer is the best. If you need to block Air in the minor leagues, you need to block it in bulk, and reflecting bulk is fun (and powerful). The dual-duties are generally (if not always) too weak to come out ahead, and the shields are probably guaranteed to fall behind. Winged Scarab arguably shouldn't be on that list at all, since its whole purpose is the Physical numbing (and the Air offense rather than defense).
if not for the under a mil i'd say the scrambler *winks to the audience* but I'm going to say the drier for the sake of it's reflecting tenencies. Why reduce when you can reflect. Call it my over offensive nature
None of them. Aside from morphing Pteri, there isn't really a good route to defend Air for less than a million (on the plus side, there's not really much that can deal Air, either).
Double Dryer is the best. If you need to block Air in the minor leagues, you need to block it in bulk, and reflecting bulk is fun (and powerful). The dual-duties are generally (if not always) too weak to come out ahead, and the shields are probably guaranteed to fall behind. Winged Scarab arguably shouldn't be on that list at all, since its whole purpose is the Physical numbing (and the Air offense rather than defense).
QFT, you mind-reader you 
Double dryer is teh useless. I voted winged scarab because it's the only thing on the list that doesn't suck.
Explain your reasoning, especially re: Double Dryer being useless. I'm curious.

Double Dryer is the best.
...
Winged Scarab arguably shouldn't be on that list at all, since its whole purpose is the Physical numbing (and the Air offense rather than defense).
Well, if you want to get technical about it, Double Dryer shouldn't be on the list either, as it reflects icons... and doesn't "block" them
High quantities of air are hard to come by at the lower levels. The most you'll probably see is 10 (from dual WoR), in which case you'd reflect 5... which is pitiful, as you'd need a 16+ iconer to be able to break even against them. With the Scarab, you'd only need an 11 iconer to do that. In any case, the majority of weapons that deal a high amount of air also deal a good amount of physical... making the Scarab the more useful choice.