AirDrop doesnt work on Macbook Air 2012 and iPhone 6S
Thanks to the development of Bluetooth 4.0 and BLE, it is not possible to airdrop between newer iOS devices and older (pre-retina, I believe) MacBooks. 

This is because the standards are incompatible, while 'legacy airdrop' is still an option for MacBook-to-MacBook communication, it appears iOS devices do not have this functionality. A more in depth discussion can be found on Apple's forums, and a lengthy discussion on whether an upgrade is possible or should be attempted here.