I just use the ASA VFR Kneeboard, I've had it for years, I clip the folded back part of the iPad Air case onto the board and it stays put.

Pros:

• Cheap
• Easy to get on and off
• Additional VFR/IFR (depending on the kneeboard) info always accessible
• Can easily be reverted to an old school kneeboard with a notepad if your iPad dies