The SIM card is removable.
http://store.apple.com/us/buy-ipad/ipad-air-2 (scroll down the FAQ)
Do all iPad models use the same type of SIM card?
No. iPad Air 2 with Wi-Fi + Cellular and iPad mini 3 with Wi-Fi + Cellular can use either the Apple SIM card or a carrier-supported nano-SIM card. iPad Air, iPad mini 2, and iPad mini use a nano-SIM card. All other iPad models use a micro-SIM card. Micro-SIM cards cannot be used in devices that use the Apple SIM or another nano-SIM card.
that doesn't really say its removable.