When a passenger plane crashed out of the sky over Iran last week, many of the world’s airlines made some urgent decisions.

At a time of already high tensions between Iran and the United States, the downing of the Ukraine International Airlines plane by an Iranian missile sealed the deal: flying over Iran was suddenly very risky.

In response, US authorities banned American airlines and pilots from flying over Iran, Iraq, the Persian Gulf and the Gulf of Oman. The European Union’s aviation agency advised airlines against flying over Iran “at all altitudes” until further notice.

Qantas said it would re-route its flights between Perth and London to avoid crossing dangerous airspace over Iran and Iraq.

Several other airlines, including Singapore Airlines, British Airways and Malaysian Airlines, made similar decisions. Flight times would be slightly longer, but paths thought the Middle East would be replotted to skirt around freshly risky spots.

Not all airlines followed suit, however. As recently as today, several carriers continue to cross Iran’s airspace, including FlyDubai, Turkish Airways, Oman Air and the popular Qatar Airways, which admittedly has limited path options since its planes were banned from Emirati, Saudi Arabian, Bahraini and Egyptian airspace in 2017.

Aviation-security experts say the biggest risks to commercial planes are portable, shoulder-carried weapons that could target jets during takeoff and landing when they’re closest to the ground, according to an Associated Press report.

More sophisticated technology would threaten planes at cruising altitude. That happened in the crash of MH17, the Malaysian airliner that was shot down in 2014 as it cruised over Ukraine at 33,000 feet.

Iran and Ukraine aren’t the only places considered risky flying zones.

The independent resource Safe Airspace pulls together risk warnings for travel in various countries, based on directives from national aviation bodies and other data.

According to the website, these are the riskiest places in the world to fly over.

It’s worth noting Australia’s civil aviation body does not issue no-fly directives to Australian airlines like the US and other countries do.

LEVEL 1: RISKIEST COUNTRIES

Iran

Since January 8, US, Canadian, UK, French and Ukrainian authorities have banned respective operators are prohibited from flying over Iran or entering Iranian airspace.

Libya

Due to civil war in Libya, and recent air strikes targeting Tripoli airport, the country is considered top risk. German and Malta has banned flights in the northwest of the country. US, French and UK carriers are told to avoid Libyan airspace.

Syria

War-ravaged Syria, currently considered the most dangerous country on earth, is a no-fly zone for at least 94 per cent of the world’s air traffic.

Iraq

Since January 7, the US, Ukraine, France, UK and Canada have told operators they should not enter Iraqi airspace.

Yemen

Yemen is also on the list, due to ongoing conflict and recent ground to ground missile attacks into Saudi Arabia. The US, Germany, France and UK say mainland Yemeni airspace is off limits.

LEVEL 2: SOME RISK

Ukraine

The risk of arms fire, such as in the downing of MH17, and issues surrounding disputed airspace over Crimea, has made flying over parts of Ukraine risky. The US Federal Aviation Administration, for example, warns aircraft risk “receiving confusing or conflicting air traffic control instructions” from both Ukraine and Russia air traffic controllers in that region.

Egypt

Egypt’s troubled Sinai Peninsula is of most concern to foreign governments. Ireland, the US and Germany urge airlines to avoid flying over the Sinai Peninsula below 26,000 feet.

Venezuela

The US has banned flying below 26,000 over Venezuela, which is in the midst of ongoing political, economic and social crisis.

North Korea

The US prohibits flights in all North Korean airspace, with France and Germany advise caution.

Pakistan

Foreign governments urge caution flying in or over Pakistan, especially at low flying levels.

South Sudan

Foreign authorities have urged carriers to be cautious below 26,000 feet in South Sudan, which remains gripped by civil war.

Saudi Arabia

Areas where foreign authorities urge carriers to exercise caution in Saudi Arabia include the southwest region and the area near the border with Yemen.

Somalia

Airlines are urged not to fly below 26,000 or 25,000 feet due to ongoing conflict and the unstable position situation in Somalia.

Kenya

Airlines are urged to avoid flying below 26,000 feet in Kenya, which is affected by civil conflict in Somalia.

Sudan

France is the only country with a warning in Sudan, and recommends aircraft do not fly below 20,000 feet in Sudan’s southern and western edges.

Afghanistan

Germany and the US warns of risks to flights under 33,000 feet and for France and the UK, it’s 24,000 and 25,000 respectively.

Mali

The US, Germany, and the UK have warnings in place in Mali, advising to operate above 25,000 feet or higher, and avoiding certain airports.

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