U.S. aviation officials have ordered Porter Airlines to trim its weekday schedule for flights from Toronto to Newark, N.J.

The changes, which take effect June 20, come less than two months after the airline launched the service between Toronto Island and the New York City area.

The order comes from the U.S. Federal Aviation Administration as part of a plan to reduce congestion at the airport in Newark.

Porter Airlines plans to cut five return flights to Newark — one flight per day — during the work week, but it's compensating by increasing its flights to that city on weekends. It will offer an additional return flight on Saturday and two extra return flights on Sunday.

In a release Tuesday, the airline said it's also adding one Toronto-Montreal return flight Monday through Friday during the busy afternoon period. This route increases to 10 return flights from nine every weekday.

During the summer, there will be eight return flights for Montreal-bound passengers leaving the Toronto City Centre Airport every weekday, up from seven.