I do have an iPad Air 2 now, but did have an Air 1 and it behaved in the same way.
I did a lot of testing and the only common thing I could find in the iPad, iPad Mini, iPhones that I had available to me was that there seemed to be a difference between the 32bit and 64 bit devices .. the newer 64 bit devices allowed less concurrent bluetooth connections.
All 64 bit devices allowed 2 Bluetooth connections
All 32 bit devices allowed 3 Bluetooth connections
I tested the following devices:-
iPad Air 1 – 64 bit
iPad Air 2 – 64 bit
iPone 5s – 64 bit
iPhone 6- 64 bit
iPad Mini – 32 bit
Show More...iPad Mini – 32 bit
iPhone 5 – 32 bit
iPhone 5 – 32 bit
since iOS 8.3 the iPad Air and iPhone 6 will now allow me to connect all three of my H9's and in the case of my iPhone and other device as well.
I have not gone back and tested the 32 bit devices and no longer own the iPhone 5S or iPad Air 1