“We were on the plane about an hour, having dinner, and then something fell on my head, so I grabbed it,” passenger Richard Bell told CBS in a Skype interview on its website.

United Airlines found itself on the defensive again on Friday after a passenger complained that a scorpion stung him during a flight from Texas, capping off a bruising week for the public image of the one of the world's largest carriers.

A man on board a United flight from Houston to Calgary, Alberta on Sunday, said a scorpion dropped on his head from an overhead storage bin and stung him under his fingernail, according to media reports.

“We were on the plane about an hour, having dinner, and then something fell on my head, so I grabbed it,” passenger Richard Bell told CBS in a Skype interview on its website.

Mr. Bell said another passenger who was Mexican told him, “'Hey, that's a scorpion, they're dangerous,' ... That's when it stung.”

United flight attendants helped the passenger after he was bitten “by what appeared to be a scorpion,” airline spokeswoman Maddie King said in an email on Friday, adding that a physician on the ground assured the crew that “it was not a life-threatening matter.”

United is “reaching out to the customer to apologize and discuss the matter,” she said.

The airline spent the week scrambling to contain the fallout from a video that emerged on social media showing security officers dragging a bloodied passenger off an overbooked United Express flight in Chicago on Sunday as other travelers looked on in horror.

Dr. David Dao, a 69-year-old Vietnamese-American doctor, suffered a concussion and broken nose when dragged from the plane and will likely sue, his attorney said on Thursday.

His lawyers have filed an emergency request with an Illinois court to require the carrier to preserve video recordings and other evidence related to the incident.

After the incident triggered international outrage, United Chief Executive Oscar Munoz apologised to Dao, his family and its customers, saying the carrier would no longer use law enforcement officers to remove passengers from overbooked flights.