International airlines steered clear of Iraq on Friday after Washington banned American air carriers from Iraqi skies in the immediate wake of US air strikes on Islamist fighters.

Flights to and from the Gulf and beyond, which typically would have taken airways through Iraq, favored parallel routes via Iran instead, according to real-time flight tracking websites.

Flightradar24.com indicated a long stream of airliners Friday evening Middle East time, flying single file through western Iranian -- and virtually none over Iraq, in a complete reversal from a month ago.

"We're still seeing some non-US carriers that are overflying Iraq," notably regional and domestic ones, added Daniel Baker of US-based FlightAware.com.

"By and large, though, we are seeing a lot of people going further to the north" and over the Turkish-Iran border, avoiding Iraq as well as war-torn Syria, he told AFP.

The Federal Aviation Administration in Washington (FAA) banned all US civilian flights over Iraq just hours after American warplanes bombed positions held by Islamic State insurgents, who have occupied swathes of northern Iraq.

British Airways declared it would no longer overfly Iraq, as did Lufthansa and its subsidiaries Austrian Airlines and Swiss -- joining Air France, Emirates, KLM Royal Dutch Airlines and Virgin Atlantic, which had quietly opted to do so over the past two weeks.

In a Notice to Airmen (NOTAM), the FAA cited the "potentially hazardous situation created by the armed conflict" between Islamic State militants and Iraqi security forces "and their allies" as the reason for the indefinite ban.

The ban extends to "all US air carriers and commercial operators," as well as US-licensed pilots unless they are flying aircraft registered in the United States for a foreign operator.

Chiefly affected by the FAA's NOTAM are Delta and United Airlines, which both serve Gulf destinations from the United States -- although flight tracking websites indicated Delta was already flying detours around Iraq.

"Very, very few flights from the United States fly over Iraq in the first place," FlightAware's Baker said.

'Exercise caution'

However, the air lanes over northern and eastern Iraq have typically been favored by international carriers for long-haul flights between Europe, the Middle East and Asia, despite many years of turmoil on the ground.

In a NOTAM dated July 22, the Iraq Civil Aviation Authority urged all pilots to "exercise caution... due to an increase of military operations from the ground to 23,500 feet (7,162 meters)."

And last week the European Aviation Safety Agency (EASA) told EU carriers to "exercise caution" over Iraq, saying "a potentially hazardous situation may exist" due to armed conflict.

Eurocontrol, the EU air traffic control service, reposted the FAA's NOTAM on its website Friday, without announcing any restrictions of its own.

Jitters about flights over war zones escalated after the July 17 downing of Malaysian Airlines Flight 17 between Amsterdam and Kuala Lumpur above an area of eastern Ukraine controlled by Russian-backed separatists.

All 298 passengers and crew were killed after the Boeing 777 was knocked out of the sky by a ground-to-air missile, allegedly by rebels targeting a Ukrainian military aircraft.

On the heels of Friday's FAA announcement, British Airways said it was "temporarily suspending our flights over Iraq" and using alternative routes to serve such Gulf points as Doha and Dubai.

Turkish Airlines, one of the key foreign carriers flying to Iraq, meanwhile said it had halted flights to Arbil "for security reasons until further notice," following a similar announcement Thursday by Etihad Airways.

Last month, the FAA prohibited US airlines from overflying eastern Ukraine in the wake of the Malaysian Airlines tragedy, expanding a ban it had previously limited to Crimea.

It also briefly barred US air carriers from Tel Aviv after a Hamas rocket fell near the Israeli city's Ben Gurion airport in the midst of the Gaza crisis.