Here's the information posted on the Port Authority's website:
""AirTrain Service Disruption
July 17 – August 19
9:00 p.m. – 7:00 a.m., Sunday to Friday
AirTrain JFK service will operate ONLY between Jamaica Station and Federal Circle. Please allow extra time to travel at JFK during this period.
Shuttle bus services will be in effect at:
Howard Beach Station
Lefferts Boulevard
Federal Circle
All airline terminals
Passengers traveling to Rental Car pick-up, Long Term/Employee parking lots will need to take the free shuttle bus service."
Here's the information