American Airlines pilots' union told its members not fly to Venezuela after the State Department warned about crime and unrest there and pulled its diplomatic staff from the country, threatening to further isolate the South American nation that is mired in a humanitarian crisis.

Most U.S. airlines halted service to Venezuela amid political and economic turmoil there. American is the last major U.S. airline to fly to Venezuela and sells flights from Miami to Caracas and to Maracaibo.

Venezuelan President Nicolas Maduro cut ties with the U.S. in January after Washington recognized opposition leader Juan Guaido as the country's president. More than 50 other countries have recognized Guaido as the country's president.

The U.S. State Department on Tuesday said it suspended operations of the U.S. Embassy in Caracas. The warning instructed U.S. citizens in Venezuela to leave the country. It has previously told U.S. citizens not to travel there.

"Do not travel to Venezuela due to crime, civil unrest, poor health infrastructure, and arbitrary arrest and detention of U.S. citizens," the State Department said in its warning.

"Until further notice, if you are scheduled, assigned, or reassigned a pairing into Venezuela, refuse the assignment" and call chief pilots, the Allied Pilots Association, which represents about 15,000 American Airlines pilots, said in a note to its members late Thursday.

American Airlines did not immediately respond to request for comment. The airline's two flights from Miami to Caracas were canceled on Friday, the airline's website showed, but flights scheduled for Saturday appeared as scheduled.

The Association of Professional Flight Attendants that represents American's 25,000 flight attendants said it supported the pilot union's decision "100%."

"Of course without the pilots, the flight's not operating," said Lori Bassani, APFA's president.

United Airlines and Delta Air Lines ceased service to Venezuela in 2017.