Boeing is threatening to lock out its private force of firefighters who protect its aircraft-manufacturing plants in the Seattle area and bring in replacements beginning Friday night unless the workers accept the company’s last offer on wages.

The company said the two sides were far apart in negotiations. It described the lockout as a precautionary move because the union could go on strike at any time once the current contract expires at midnight local time.

Each side accuses the other of bad-faith negotiating.

The labor showdown comes as Boeing deals with mounting losses — more than $24 billion since the start of 2019 — and increased scrutiny over quality and safety in its manufacturing since a door plug blew out of an Alaska Airlines Boeing 737 Max flying over Oregon in January.

On Friday, Boeing dismissed any safety concerns about the dispute with its industrial firefighters. The company said it has made arrangements with “highly qualified firefighters” to replace the union workers, and the lockout will not affect operations at plants where it builds planes.