NEBRASKA — Tianrui Liang, 21, was arrested April 7 at a New York airport and charged with illegally photographing U.S. military aircraft at Offutt Air Force Base in Nebraska. Liang was attempting to leave the United States for Glasgow, Scotland, where he attends school, according to a court filing.

Liang was charged in connection with taking photos of U.S. military planes in Nebraska during a multistate road trip that included a stop at an Air Force base in South Dakota. In late March, he got out of a car on a public road and took photos of an RC-135 reconnaissance aircraft and an E-4B at Offutt Air Force Base near Omaha, the court filing said.

The E-4B, known as the "Nightwatch," can serve as an airborne command center for a president and military officials in times of emergency, according to the Air Force. It is illegal to photograph or sketch defense installations without approval, the court filing said.

Liang flew to Vancouver, British Columbia, on March 26 and met a friend who is a college student in New York, according to the filing. The two drove across the U.S. border in Washington state. Liang later drove alone to see Ellsworth Air Force Base in South Dakota.

Liang told investigators that taking pictures of the planes on the ground was illegal, although taking pictures of the sky is legal, the filing said. He told investigators he took the photos for his personal collection and that he was interested in going to Tinker Air Force Base in Oklahoma.

Liang has not yet appeared in federal court in Omaha. No attorney of record for Liang was listed in the court filing.