American Airlines pilots have refused to fly to Venezuela, citing the ongoing unrest in the South American nation, leading the airline to cancel all flights to Caracas and Maracaibo.

The San Jose Mercury News reports that the airline announced the temporary suspension of service, stating, “American will not operate in countries we don’t consider safe.”

Unions representing the airline’s pilots and flight attendants both called for a halt to American’s Venezuela flights.

“I will not put our crews in harm’s way and we support the pilots’ decision not to fly into Venezuela due to escalation of political unrest,” flight attendants union president Lori Bassani wrote to American CEO Doug Parker.

The airline is the only major US carrier to fly to Venezuela. American usually flies twice daily between Caracas and Miami and once daily between Maracaibo and Miami.

Venezuela is currently in the midst of a constitutional crisis pitting its socialist leader against an opposition politician who has asserted that he is the rightful leader of the country. The U.S. State Department has warned against travel to Venezuela and has pulled its diplomats out of the country.

Power outages also have affected the Caracas airport, delaying flights and causing travellers to endure long waits.