Why Did Kim Jong-un Travel by Train?

North Korean leader Kim Jong-un took a special train when he secretly visited China early this week, a move reminiscent of his father Kim Jong-il.

Kim senior had a notorious fear of heights and simply avoided flying. Every domestic trip and even those to China and Russia were always by rail.

Some might have thought Kim Jong-un to be different. He has taken planes many times while inside North Korea -- even taking photographs in a pilot's uniform. But he, too, chose to travel by train on his recent visit to China.

It turned out he may not have had much of choice. UN Security Council sanctions make it mandatory to search the cargo of all flights departing from North Korea, and Kim's plane, which belongs to Air Koryo, is under U.S. sanctions. But train travel can evade such sanctions.

However, using trains could make it difficult for China as they may require even more heightened security. "All the railroads and stations have to be closed off for Kim's train to pass," a researcher at a state-run think tank said. "Kim may have wanted to boast that he could get special treatment from China."

The train is also extra secure, including bulletproof glass. The train also seems to have been remodeled by Kim Jong-un as it sports a slightly different registration plate, although it looks very similar to the one used by Kim Jong-il.