Singapore Airlines, Qantas, China Airlines, Lufthansa and Malaysia Airlines were among those which said they're avoiding the Iranian airspace.

Meanwhile, Dubai-based Emirates and its sister airline flydubai canceled Wednesday flights to Baghdad.

"We are carefully monitoring the developments and are in close contact with the relevant government authorities with regards to our flight operations, and will make further operational changes if required," Emirates said in a statement to Reuters.

The announcements came after Iran launched more than a dozen ballistic missiles against multiple bases housing U.S. troops in Iraq.

Tehran's attack follows the U.S. killing of Iran's top general, Qasem Soleimani, last Friday. Tensions in the Middle East rose following his death, with Iran vowing revenge.

"We are monitoring the situation closely and will make the appropriate adjustments to our routes if necessary," it added.

Taiwan's China Airlines also said it will not fly over Iran or Iraq due to regional tensions, Reuters reported.

Australia's Qantas told CNBC it was adjusting flight paths in the Middle East to avoid airspace over Iran and Iraq and would reroute its QF9 and QF10 flights between London and Perth via Asia.

British Airways told CNBC in a statement it was in "constant contact" with partners around the world  to assess security of its routes while German flag carrier, Lufthansa, confirmed it had canceled today's flights to and from Tehran. 

"As soon as we have detailed information, we will decide if and when flight operations to/from Tehran and Erbil can be resumed," it added.

The largest carrier in Taiwan, China Airlines, said in a statement to Reuters that it will continue to monitor the situation and adjust routes accordingly.

Another Taiwanese airline, EVA Air and Malaysia Airlines also said they're avoiding flying over Iran airspace, Reuters reported.

Meanwhile, the U.S. Federal Aviation Administration issued notices on Tuesday night outlining flight restrictions that prohibit U.S. civil aviation operators from operating in the airspace over Iraq, Iran, and the waters of the Persian Gulf and the Gulf of Oman.

"The FAA will continue closely monitoring events in the Middle East," it said in a statement. "We continue coordinating with our national security partners and sharing information with U.S. air carriers and foreign civil aviation authorities.

Outside of Asia, Transport Canada said Air Canada has also changed its routes.

"Air Canada, the only Canadian air carrier that operates in the region covered by the FAA NOTAM, has altered its routes to ensure the security of its flights into and over the Middle East," the transport authority said.

Transport Canada is in close contact with the FAA, it added.

In a separate incident Wednesday, a Boeing 737 operated by Ukraine International Airlines crashed shortly after take-off from Tehran's Imam Khomeini International Airport on Wednesday morning, killing 167 passengers and nine crew members.