On the same day that a passenger was dragged off a United Airlines plane, a stowaway made it onto another flight.

A scorpion, found on a plane flying from Houston to Calgary on Sunday (April 9), fell on a man and stung him, CNN reported.

It was the same day Dr David Dao, a 69-year-old Vietnamese-American doctor, was manhandled and dragged from another United Airlines flight, stirring up a media maelstrom that has barely abated.

The poisonous creepy-crawly fell from an overhead cabin in the business class and landed on the head of passenger Richard Bell as he was eating lunch.

"My husband felt something in his hair. He grabbed it out of his hair and it fell onto his dinner table. As he was grabbing it by the tail, it stung him," his wife Linda Bell told CNN.

United Airlines (UA) said in a statement that its flight attendants helped "a customer who was stung by what appeared to be a

scorpion on a flight last week".

"Our crew immediately consulted with a MedLink physician on the ground who provided guidance throughout the incident and assured our crew that it was not a life-threatening matter," said UA in the statement given to CNN.

Medical personnel met the aircraft when it arrived in Calgary, the airline added.

Mr Bell shooed the scorpion off his tray, and it fell into the aisle.

Flight attendants trapped it and flushed it down an airplane toilet. It's not clear how the scorpion made it onto the plane.

Mrs Bell said United apologised to her husband and offered compensation for the incident.

Animals have made it onto other flights undetected.

In January, an Emirates flight from Muscat to Dubai was cancelled after baggage handlers discovered a snake in the aircraft's cargo hold.

In August last year, a small rodent, probably a mouse, caused the grounding of an Air France flight from Bamako to Paris.

CNN reported another case of a scorpion in 2015, this time on an Alaska Airlines from Los Angeles to Portland.