United Airlines on Friday found itself on the defensive again 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 onto his head from an overhead storage bin and stung him under his fingernail, according the United and 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.