Four more Bombardier jets must fix their oxygen bottles

The US aviation regulator is expanding a mandatory fix for faulty portable oxygen bottles on certain Bombardier airplanes. This means more aircraft owners will have to check and potentially modify their planes to prevent an unsafe condition.

Airworthiness Directives are how the Federal Aviation Administration ensures planes remain safe to fly. When an AD is issued, it means a specific problem has been identified that could put passengers or crew at risk. Expanding an existing AD means the problem was more widespread than initially thought, forcing more owners to take action.