United States special envoy for climate John Kerry was spotted without a mask, while he was on board a flight from Boston to Washington DC, reported The Hill. The photograph of Kerry reading a book with his mask hanging off his ear was shared on social media on Wednesday.

Also read: CDC removes mask mandate for fully vaccinated people

Former US president Donald Trump's son, Donald Trump Jr, also shared the photograph, who dubbed the climate envoy as a "liberal hypocrite."

"His mask is off & he isn’t eating or drinking. Will he be fined for breaking the law & banned from flying @AmericanAir like regular citizens would be?" Trump Jr tweeted.

Responding to the criticism he received, Kerry on Wednesday tweeted, "Let’s be clear: If I dropped my mask to one ear on a flight, it was momentary."

"I wear my mask because it saves lives and stops the spread. It’s what the science tells us to do," he added.

American Airlines too responded to a tweet about the picture. It said, "Masks are required on board our aircraft, and we are looking into this."

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As per coronavirus-related rules, everyone above the age of two needs to wear mask on flights of airlines under federal guidance.