A recent tragedy would have been avoided if all airlines followed American advice. On July 17th a Malaysian airliner (flight MH17) flying over eastern Ukraine was shot down as it passed over territory controlled by pro-Russian separatist rebels. The airliner was at an altitude of 10,000 meters and the rebels were known to have some captured anti-aircraft systems (BUK M1s) that can hit targets as high as 14,000 meters. Before MH17 was shot down most airlines rerouted their flights between West Europe and points east away from eastern Ukraine, just to be on the safe side. This increased flight time and cost, but was considered prudent. Malaysian Airlines and a few others did not reroute because, technically, there was no official warning that the airspace over eastern Ukraine might be dangerous.
Before July 17th the U.S. FAA (Federal Aviation Authority) had warned airlines to avoid flying over the Crimea and cautioned against crossing eastern Ukraine. On July 18th eastern Ukraine was added to the FAA “avoid” list. Other areas the FAA warns airlines about are Iraq, North Korea, Ethiopia (the north), Somalia, Libya, Afghanistan, Congo, Kenya, Egypt (Sinai), Syria and Yemen. Most of these areas are only subject to warnings, usually about avoiding flying under 6,000 meters (staying out of range of shoulder fired missiles and heavy machine-guns). But for Crimea and eastern Ukraine, Iraq, North Korea, northern Ethiopia and Somalia airlines are advised to stay away unless they have to go and are very careful (take off and land quickly and stay high, over 6,000 meters).
The U.S. government, especially the State Department, closely monitors local conditions worldwide and regularly sends warnings of areas where it is dangerous and Americans should not travel to unless necessary and then with much caution. The FAA, and other U.S. government agencies, issue similar warnings when an international terrorist threat shows up during their constant monitoring of worldwide threats that might get into the United States.