Q: How to transfer photos from iphone6 to iPad air

You don't.  You import them to your computer as you would with any digital camera.

Import photos and videos from your iPhone, iPad, or iPod ...

You can e-mail them to yourself or use photo stream to access them from the cloud on both devices.

You can transfer photos from an iPhone 6 to an iPad Air via WiFi using AirDrop: Use AirDrop to wirelessly share content - Apple Support

or an app like Photo Transfer:

Photo Transfer App - Easily copy, share and backup pictures and videos over wifi between devices and computer by ERCLab, LLC

https://appsto.re/us/SQ8Wv.i

It is also possible to transfer the photos using the USB Camera Adaptor: http://store.apple.com/us/product/MD821ZM/A/lightning-to-usb-camera-adapter?fnod e=3a

Another option that is fairly new and that I haven't tried myself yet but may be of interest: iCloud Photo Library beta FAQ - Apple Support

AirDrop  is a good way to do that...

Use AirDrop to wirelessly share content - Apple Support