The Swiss International Airlines flight declared a mid-air emergency
The Swiss International Airlines flight took off from Zurich at around 8.20am GMT.
But flight monitoring systems say the flight LX400 declared an emergency changed its course an hour into the journey.
The plane was forced to land at Brussels due to a medical situation on board.
Swiss flight LX400 bound for Dublin will divert to Brussels airport due to an onboard medical case
Swiss Airlines spokesman
A spokesman from Swiss Airlines said: “I can confirm that SWISS flight LX400 bound for Dublin will divert to Brussels airport due to an onboard medical case.
“The plane is carrying 153 passengers and nine crew members.”
The flight landed shortly before 10am GMT.