Qantas has announced it will be redirecting one of its longest international routes over fears tensions in the Middle East could boil over and make it unsafe to fly over the region.

The Australian carrier's decision follows a number of other airlines suspending or altering routes as the threat of a broader conflict between Israel, Iran and Lebanon intensifies.

In recent weeks, Israel has assassinated Hezbollah commander Fuad Shukr in the Lebanese capital Beirut and hours later is believed to have killed Hamas leader Ismail Haniyeh in the Iranian capital, Tehran.

Iran has vowed to retaliate for the killings, prompting fears of air strikes on Israel and a larger regional war.

Qantas' service from Perth to London, which usually takes around 17 hours nonstop, will now make a refuelling stop in Singapore to allow it to carry extra fuel and take an alternative route onwards to London.

The return leg is unaffected by the changes, as are direct Qantas services between Perth and Paris, and Perth and Rome.

"We'll contact customers directly if there's any change to their booking."

It is not the first time Qantas has made such a call during the recent conflict in the region, with a similar decision being made in April and in 2020 in the wake of missile strikes on US bases in Iraq.

While a relatively minor change to Qantas' operations, the decision is indicative of deepening concern about safety across busy Middle East airspace in the event Iran or Lebanon launch attacks on Israel in coming days.

The memory of Malaysia Airlines flight MH17, shot down by Russian-backed forces over Ukraine more than a decade ago, continues to loom large for the international aviation industry.

Airspace warnings

Qantas' announcement comes as other airlines and countries suspend flights and issue their own warnings.

Air France extended its suspension of flights between Paris and Beirut until August 11, while Italy's ITA Airways further extended its pause on flights to and from Tel Aviv until August 10.

US-based United Airlines and rival Delta Air Lines have also stopped their Tel Aviv flights.

Egypt on Wednesday issued a NOTAM — a safety notice provided to pilots — instructing all of its airlines to avoid Tehran's airspace for three hours early on Thursday morning, later saying it was due to an Iranian military exercise taking place.

Hours later, Britain also issued an advisory to its carriers to avoid Lebanon's airspace. Flight-tracking websites now show no commercial planes are flying to the country.

Similarly, Singapore Airlines stopped flying through Iranian airspace last Friday and is using alternative routes.

On Sunday, Jordanian authorities asked all airlines landing at its airports to carry 45 minutes' worth of extra fuel.

Countries in the region, including Jordan, closed their airspace in April amid Iran's aerial attacks on Israel.

In 2020, Iranian air defence units said they mistakenly shot down Ukrainian International Airlines flight PS752, killing all 176 people on board, shortly after it took off from Tehran airport. At the time, they were on heightened alert because of increased tensions with the United States.

A region on edge

All eyes are on Iranian and Lebanese officials after Israel killed the Hamas and Hezbollah top brass in Tehran and Beirut.