Voting opened on May 1 in the previously-announced Southwest Airlines Pilots Association's (SWAPA) strike authorisation vote.
The"historic vote", SWAPA said, is to run until the end of the month and is being held "in the wake of Southwest's epic December meltdown and after three years of negotiations with the company".
"We have been attempting to negotiate with Southwest in earnest for years, but they have shown no willingness to address some of the issues that impact not only our pilots but our customers as well, such as scheduling work rules and technology improvements. It is essential that we modernise systems and procedures to be able to keep pace with other carriers and give our passengers the level of service they expect," said SWAPA president Casey Murray.