Several airlines, including United Airlines, British Airways, Virgin Atlantic and Singapore Airlines, are rerouting aircraft to avoid airspace over Afghanistan after the Taliban seized control of the country.

According to a notice to pilots from Afghanistan aviation officials, air traffic control has been handed over to the military and planes will be "flying in uncontrolled airspace at their own risk," CNBC reported. As of last month, the Federal Aviation Administration (FAA) prohibits U.S. airlines from overflying Afghanistan air space below 26,000 feet (well below cruising altitude) "due to the risk posed by extremist/militant activity and limited risk mitigation capabilities."

"Due to the dynamic nature of the situation we have begun routing affected flights around Afghanistan airspace," United said in a statement regarding its U.S.-India flights, adding that it "will continue to work closely" with the FAA and the International Air Transport Association (IATA) "to evaluate the situation and determine how we continue service to markets impacted."

United is the only major U.S. carrier operating nonstop flights to India, flying from Newark to Delhi and Mumbai daily and from Chicago to Delhi five times a week.

Other airlines, including Emirates and Flydubai, have suspended flights to Afghanistan's capital city of Kabul amid the turmoil. "Customers holding tickets with final destination to Kabul will not be accepted for travel at their point of origin," according to Emirates.

In an alert published Monday, the U.S. Embassy in Kabul reported that "the security situation in Kabul continues to change quickly, including at the airport. There are reports of the airport taking fire; therefore we are instructing U.S. citizens to shelter in place."

Afghanistan continues to receive a Level 4 (Do Not Travel) travel advisory from the U.S. State Department, which warns of "COVID-19, crime, terrorism, civil unrest, kidnapping and armed conflict."