American Airlines said Monday it had contacted Republican Senator Ted Cruz after he was seen without a mask on a flight, but he said he had only removed it to eat and drink.
Health experts and scientists have called on politicians to set an example by wearing face coverings as the coronavirus rages across the United States.
"While our policy does not apply while eating or drinking, we have reached out to Senator Cruz to affirm the importance of this policy," American Airlines said in a statement.
The Texas lawmaker was holding a coffee cup and a phone in the widely-shared photo, but there was no mask in sight.
"During his flight he removed his mask to drink and put it back on afterward," a spokeswoman for Cruz said. "We should all practice common sense measures to slow the spread of the virus."
Wearing a mask in the United States has become a heavily politicized issue in recent months.
President Donald Trump was only seen in one for the first time on Saturday when visiting a military hospital.
Texas's Republican governor Greg Abbott has made wearing masks in public places mandatory -- a measure he long resisted putting in place.