Zone 6A. Too late to start an air layer?  

Takes about 5 weeks . So why not ?
The roots will keep growing till soil temp goes below apx 45F

John

Never too late.  Folks will tell you that you're "supposed" to do it while the tree is actively growing, but I have setup airlayers late in the year last year (just before dormancy) and they finished in about 8 weeks, after dormancy, and continued to root during dormancy.  I've also done them in spring - had to do several this year to produce trees for our community garden, this was right when things started leafing out, most finished in less than 5 weeks. 

just completed my first air layer. It was only a Celeste but the growth was split between the top and the bottom so it was a perfect candidate. 

soaked peat moss for 2 hours. Cut a Gatorade bottle in half. Used plastic wrap to seal the top and bottom. Used zip ties to make sure it was air-tight. 

squeezed a tiny bit of water out of the peat moss and packed it in the bottle. I also cut off 1 inch of the bark all around to encourage root development. Then wrapped the whole thing in foil. Excited to try something new. 

I have a HC that is screaming for an air layer but I'd like to get it right before I do it. 

Not too late at all. Try to set your air layer(s) within the next week or two. Some fig varieties root early and others a little late. Today I removed several nicely rooted air layers off my Sequoia fig that I set 3 weeks ago!  

I just started mine a couple weeks ago, and have more to do, yet.