United Express Flight 4890, operated by Republic Airlines, took off from Newark en route to Pittsburgh but turned around after smoke flooded the cockpit.
The plane landed without incident and was surrounded by emergency vehicles on the runway.
No injuries were reported, and a few dozen passengers taken off the plane and moved to waiting buses.
Responders accessed the plane and were evaulaitng what went wrong.
Landings and departures were temporarily suspended and runway 4R shut down, but the air space remained open.
Normal service resumed just b efore noon.