It's more than possible that FedEx, UPS, etc. might have laid on a few extra planes for this sort of event.
Which brings up an interesting question: How many iPads can a typical commercial freighter carry?
The 777 freighter has a rated cargo capacity of 243,000 lbs. Given an average shipping weight of a packaged iPad of about 2 lbs, that would suggest almost 100,000 iPads per plane. But how does the "cube" work out?
The stated cargo cube of a 777 is 37 standard shipping pallets: Each standard pallet is 96 x 125 x 120". A packaged iPad is roughly 10" x 8" x 2". Each tier on each pallet would hold 144 iPads, and assuming 9.5' of height, gives us 57 tiers. Roughly 5,000 iPads per pallet. (Each pallet is worth approximately the same as a modestly priced US home..)
So, yeah: Roughly 100,000 iPads per plane seems at least plausible. (Please, any commercial freight experts feel free to correct any errors in my back-of-the-envelope math).
Given a worldwide launch-day sell-through of 5 million units, that would imply an extra 50 aircraft. Given the fact that Hong Kong International (the hub closest to Shenzhen) has roughly 300,000 departures and arrivals per year (thats a thousand a day) - I don't think an extra fifty planes over the course of a week is going to throw things into utter chaos.
At 100,000 iPads per plane, the cargo alone has a value of roughly half a billion dollars. Or almost twice the list price of the airplane itself ($280 million.)
We've had our iPad 2 a couple of months now but were prepared to upgrade. I'm not doing it because the iPad 3 isn't an "iPad 3" plus it doesn't even have Siri or more memory.
