Virgin America airline flight attendants are due to begin voting next month on whether to organize, potentially bringing the first union to the California-based airline.

The balloting by about 850 eligible flight attendants on representation by the Transport Workers Union (TWU) is due to begin July 16 and run through August 16, the union and the National Mediation Board said on Wednesday.

Approval of the union would further narrow the ranks of non-union U.S. carriers, after JetBlue pilots voted in April to organize, ending the non-union status at that airline.