Cathay Pacific Airways is implementing new inspection protocols and taking some staff off flight duties as the Hong Kong-based carrier continues to investigate how oxygen bottles were emptied on three aircraft in recent weeks.

During preflight checks on the affected aircraft, some portable oxygen bottles were discovered to be partially or fully emptied. The portable bottles are for use by crew members in emergency situations. There are no indications yet as to how the bottles were discharged, or who was responsible. One aircraft was operated by subsidiary Cathay Dragon.

In a memo to staff, Cathay said it is “taking this issue very seriously and all cabin crew on the flights involved will be temporarily placed on the code DA while the investigation is conducted.” Code DA refers to “duty to be assigned” and effectively means suspension from flight duties. The airline said this step, applied to three flight crews, is intended “to facilitate investigations.”

Cathay said the incidents are being investigated internally, and by police and regulatory authorities in Hong Kong and China. “The investigation team is following up with all relevant parties including ground staff, caterers, cleaners, engineers etc.,” the memo stated.

Cathay said cabin crew is responsible for ensuring emergency equipment is operational and safeguarding it during flight. “As such, with immediate effect, we will be implementing an inflight cabin monitoring program,” the memo stated. This will require crew to check the cabin, lavatories and crew rest areas at least every 60 min., “ensuring no suspicious activity.” Crew are also directed to “be extra vigilant to emergency equipment stowage areas.”

A notice to cabin crew included a list of things to monitor, including “abnormal smell, noise or temperature” in the cabin or crew rest areas.

The airline is also strengthening procedures for checking emergency equipment between flights. These checks will apply to all flights, both after disembarking passengers and preflight.

“We always conduct preflight inspections before every flight,” Cathay said in a separate media statement. “Recently, we have further strengthened our security measures to now include preflight, inflight and post-landing checks for every flight to ensure all emergency equipment is serviceable so that the safety of our crew and passengers is upheld at all times.”

Adrian Schofield,