A Flybe plane carrying 44 people suffered hydraulic problems before landing at Newquay Airport.
The Dash 8 aircraft landed at 22:00 BST on Tuesday after taking off from Gatwick.
Passengers reported seeing fluid leaking from an engine. Flybe said there was a "minor technical fault".
Fire crews and police were called to the scene but airport staff dealt with it. No-one on board the twin-propeller aircraft was injured.
'A bit serious'
Passenger Matt Hulme said the crew was alerted to a problem after another passenger reported seeing fluid coming off one of the engines.
He told BBC News: "The left-hand one was really leaking fluid.
"A passenger, I think he was an ex-pilot or something, alerted the cabin crew.
"The captain told us there was a problem with the hydraulics so they were not able to steer the plane and a tug needed to tow it.
"He added that we should not be alarmed at the number of vehicles coming down the runway, and not to be alarmed by the fire engine.
"As I was picked up and taken away from the aircraft, about three or four fire engines shot past.
"That was when I thought: 'OK, that could have been a bit more serious than I first thought'."
The plane is believed to have been carrying 40 passengers and four crew.
Flybe said a warning light about a "minor technical fault" came on in the cockpit during landing.
It added that the incident was not officially classed as an emergency landing.
'Sorry for inconvenience'
It said: "It was deemed necessary that the 40 passengers disembark the aircraft on the taxiway, which they did without incident before being bussed to the terminal.
"As is standard industry practice, the airport's emergency services attended the aircraft.
"Flybe regrets the inconvenience experienced by our passengers as a result of this incident."
Although dealt with by airport fire staff, seven crews from Cornwall Fire Service and five police vehicles were called the airport.
As a result of the incident, Wednesday's 07:15 flight to Gatwick was cancelled.
One flight due to arrive from Gatwick at 10:15 has also been cancelled.