FlyDubai planes are parked on the tarmac at Dubai International Airport as Iran retaliates following the US and Israel's assassination of its supreme leader, in Dubai on Monday.

The US State Department has urged US citizens to leave the Middle East “due to serious safety risks.”

It called on US citizens to depart “using available commercial travel” from Bahrain, Egypt, Iran, Iraq, Israel, the West Bank and Gaza, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, the United Arab Emirates, and Yemen.

But the limited number of flights poses a challenge for those trying to leave.

More than 1,000 flights had already been canceled as of Tuesday morning, adding to the thousands of international flights canceled on Sunday and Monday, according to data from FlightAware.com.

Americans in Israel have “very limited options” to leave the country, said US Ambassador to Israel Mike Huckabee, warning that the US embassy was “not in a position at this time to evacuate or directly assist Americans” in leaving the country.

Outside the region, other airlines continue to reroute or cancel flights that had been scheduled to fly near the conflict zone. The skies over the UAE, Qatar, Kuwait, Israel, Bahrain, Iraq and Jordan all remained nearly empty Tuesday morning, as shown on maps by flight tracking website Flightradar24.

A small number of flights left the United Arab Emirates late on Monday but at least one that attempted to fly from India to Dubai was forced to turn around.

Other governments, including Canada, the United Kingdom and Australia, are also telling their citizens to avoid the region.