@Susan335 When I was new to this game and had multiple properties, I used a PAPER (gasp) calendar and marked in colors when a property was booked -- yellow for one, blue for another, green for another, you get the idea. It was easy, simple and clarified for me when housekeeping needed to be scheduled.
I don't have multiple listings on Air, so I don't know how Pro Tools would help you. (I do have multiple properties on multiple OTAs.)
You can export your calendars to Google or Microsoft Outlook and then overlay each calendar. You can enter the information on any calendar in Word. You can purchase a professional property program and use their calendar (I can't recommend any) I am still using paper, and loving it.