I may have missed this in the manual so does the Mavic Air charger have the capacity to charge the drone and the transmitter at the same time or should you do one at a time?  

Yes, you can charge both at the same time.

Hello and good day. Thank you for raising this inquiry. Yes, you will be able to charge both the Intelligent Flight Battery and the remote controller at the same time using the DJI Mavic Air's original charger. When doing this process the charging time might take longer than usual compared to charging the intelligent flight battery and charging the remote controller separately using the DJI Mavic Air's original charger. If you have any other concerns with DJI. Please feel free to post it here at DJI Forum. We are here to help you.

Thank you.

you can charge them at the same time