This may have been discussed but I'm unable to find definite answer.
I got my mt4 and its been great, however since I purchased a 2nd receiver same as the one that comes with the kit, selected 2nd model and completed the binding procedure now both cars run if they are turned on. I know with spectrum what ever model you select will only run that specific model. I can see this happening with AM transmitter but hard to believe that airtronics would do this.
Is there any setting to turns this off ?
I did try to re-bind both several times no luck

Turn your other car off? Airtronics rx binding is global. Unless you have different modulation in a particular car, any rxs bound to the tx using the same modulation will work with any model.
You only have to bind airtronics receivers once. Like futaba.

I do turn it off or at least I try to remember. The other day I didn't and car went flying off the desk almost. Why would they do this with spectrum what ever model you select it only runs that specific model, I suppose i can run up to 18 models at the same time :-) and futaba is the same?

Cause not everyone has a lot of receivers for each car at $130 a peice lol.
I personally
Like it. Can swap an rx real quick and no fiddling with binding ect. Only car i forget to turn off sometimes is the nitro car.