Download the latest IPSW for the iPad Air 3 (Cellular) - iPad11,4 IPSW firmware files direct download links from Apple's server. You can use the signed versions of the firmware on this page to fix issues and reactivate disabled iPad or perform system upgrades.
This variant of the iPad Air 3 comes with BoardConfig: J218AP, Platform: t8020, BDID: 0x1E, and CPID: 0x8020. The firmware identifier is iPad11,4.