Powerjet1
The aircraft requires an Engineering A check after certain amount of flight hours. These checks are undertaken by My Travel at Manchester. The Airline will calculate when these checks are due (its not rocket science to calculate the hours based on a JFK being aprox 14 hrs per day) and then take out either a service or 2 services on a planned basis. By the sounds of it the weekends are the quieter times for JFK so they do it then.
