Boeing faces further delays to the return to service of its B737 Max aircraft, after the Federal Aviation Administration said it had found “a potential risk which Boeing must mitigate”.

Boeing’s Max aircraft are currently grounded worldwide, following two fatal crashes involving the jets, and in a statement yesterday the FAA said:

“The FAA is following a thorough process, not a prescribed timeline, for returning the Boeing 737 Max to passenger service. The FAA will lift the aircraft’s prohibition order when we deem it is safe to do so.

“We continue to evaluate Boeing’s software modification to the MCAS and we are still developing necessary training requirements. We also are responding to recommendations received from the Technical Advisory Board (TAB). The TAB is an independent review panel we have asked to review our work regarding 737 Max return to service.

“On the most recent issue, the FAA’s process is designed to discover and highlight potential risks. The FAA recently found a potential risk that Boeing must mitigate.”

Boeing has also released a statement as follows:

“The safety of our airplanes is Boeing’s highest priority. During the FAA’s review of the 737 Max software update and recent simulator sessions, the Federal Aviation Administration (FAA) identified an additional requirement that it has asked the company to address through the software changes that the company has been developing for the past eight months.

“The FAA review and process for returning the 737 MAX to passenger service are designed to result in a thorough and comprehensive assessment. Boeing agrees with the FAA’s decision and request, and is working on the required software. Addressing this condition will reduce pilot workload by accounting for a potential source of uncommanded stabilizer motion.

“Boeing will not offer the 737 MAX for certification by the FAA until we have satisfied all requirements for certification of the MAX and its safe return to service.”

Carriers including American Airlines and Oman Air have been significantly affected by the grounding of their B737 Max fleet, while Ryanair has delayed the delivery of its first Max aircraft until winter at the earliest.

Meanwhile at last week’s Paris Air Show, BA’s parent company IAG signed a letter of intent for 200 B737 Max aircraft, which subject to formal agreement would be delivered between 2023 and 2027.