The first flight, carrying 66 passengers from Toronto to Washington, D.C., was diverted to Williamsport, Pa. when smoke entered the flight deck and cabin shortly it took off at 8 a.m..
Porter spokesman Brad Cicero says the plane landed safely and another aircraft was brought in to take the passengers on to Washington.
Then Sunday evening a Porter flight bound for Sudbury, Ont. with 74 passengers aboard also had to return to Toronto because of smoke inside the plane.
Cicero says the flight crew shut down one of the Dash 8-400's two engines, according to standard procedure, and landed safely at Toronto's Pearson International Airport.
He says two passengers were seen by medical staff for suspected anxiety, and two flight attendants were also examined as a precaution.
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