There's a police check to exit the subway, another to get in line, a third while standing in line, and metal detectors and X-ray machines before you finally reach the Beijing landmark.

China has put new focus on airships hovering in a part of the sky just before outer space. Although Beijing says they're scientific, analysts say the data helps the country develop advanced weapons.

"Crews have been able to recover significant debris from the site, including all of the priority sensor and electronics pieces identified," U.S. Northern Command said.