Officials at Air China's offices in Japan said the threat called for the immediate suspension of all Air China flights and threatened to crash aircraft into the Summer Olympics site, Beijing Now reported Friday.
"We are telling Air China: immediately suspend operations of all flights," Air China officials quoted the e-mail message as saying. "Otherwise we will bomb the planes. We will crash the airplanes into the site of the Olympics."
Two Air China aircraft have been grounded and are being searched in Japan, an official at Japan's Narita airport said.
Beijing Now said China was enforcing strict security efforts in Beijing Friday for the Olympic opening ceremony. Among those efforts was the shut down of Beijing airport as a precautionary measure.