Singapore Airlines has taken steps to change the route of its Seoul-Los Angeles flights since July this year as a safety precaution in response to North Korea’s missile tests. Meanwhile, Japan is preparing to acquire precision air-launched missiles that for the first time would give it the capability to strike North Korean missile sites, sources said. South Korea and the United States launched their largest-ever joint aerial drills on Monday, a week after North Korea said it had tested its most advanced missile as part of a weapons program that has raised global tensions.