A pilots union filed a lawsuit on Thursday seeking to immediately halt American Airlines U.S.-China service, as cabin crews worldwide voiced unease about exposure to the rapidly-spreading coronavirus which has killed more than 170 people in China.

The Allied Pilots Association, which represents American Airlines pilots, cited "serious, and in many ways still unknown, health threats posed by the coronavirus."

American, the largest U.S. carrier, did not immediately comment on the suit, filed in a Texas court. The Fort Worth, Texas-based airline announced on Wednesday it would next month suspend flights from Los Angeles to Beijing and Shanghai, but continue flights from Dallas.