The airlines provide special flights, cargo hauling and other services for the government. The companies say that makes them government contractors who are covered by President Joe Biden’s order directing contractors to require that employees be vaccinated.

American Airlines CEO Doug Parker told employees late Friday that the airline is still working on details, but “it is clear that team members who choose to remain unvaccinated will not be able to work at American Airlines.”

The pilot union at American recently estimated that 4,200 — or 30% — of the airline’s pilots are not vaccinated.