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SITUATION UPDATE 13 March, 2019 Back

Situation Update - Airspace Restrictions on Boeing 737 Max Jets

Karl Kirkcaldy

Boeing Max 8


  • Approximately two-thirds of 737 Max aircraft operating globally have either been grounded or subjected to airspace restrictions.

  • Reports indicate an estimated 6000 of the 8600 flights operating in a typical week of travel are affected.

  • US Federal Aviation Administration not planning to ground the jets in the United States at this time, instead issuing a notice of mandated design enhancements to the automated systems by April 2019.

  • Boeing to expedite scheduled changes to flight-control software for the MCAS system.

  • Restrictions come amid investigations into the Ethiopian Airlines Flight 302 crash, the second 737 Max accident within 6 months after Lion Air Flight 610 crashed into the Java Sea in October 2018.

  • The Boeing 737 Max unique MCAS system is being focused on as part of the accident investigations.

  • There has been no official cause for either of the 737 Max accidents with the final reports likely to take months, possibly even years.

  • Both 737 Max 8 & 9 aircraft affected, with a total of 374operating worldwide.


A number of countries across the globe have placed restrictions on Boeing 737 Max aircraft operating in their airspace and numerous airlines have either been forced, or volunteered, to ground their fleet of this variant of aircraft. The move is understood to be out of an abundance of caution following the crash of Ethiopian Airlines Flight 302 which went down six minutes after take-off near the town of Bishoftu in Ethiopia, with the loss of all 157 passengers and crew. 

What made this accident significant is that the aircraft, a Boeing 737 Max 8, one of Boeing’s newest commercial airliners with this particular model being delivered on 15 November 2018, was the same variant as Lion Air Flight 610, which crashed into the Java Sea on 29 October 2018, killing all on board. In aviation terms and when factoring in historical analysis, this is an unprecedented occurrence in an era of increased aviation safety, underpinned by a continuous improvement in safety. 

It appears as if aviation authorities and airlines are focusing on the perceived similarities of both accidents, despite both accident investigations still being in their early stages and with no official outcome as to the cause. Again, this is an unprecedented move particularly as the aircraft manufacturer maintains that "Safety is Boeing's number one priority and we have full confidence in the safety of the Max." The FAA has also issued a statement saying the agency's review of the 737 Max "shows no systematic performance issues and provides no basis to order grounding the aircraft." 

However both the FAA and Boeing have indicated that changes will be implemented to upgrade software relating to automated flight control systems, along with updates to operation manuals and crew training. One of the unique features of the Boeing 737 Max variant of aircraft is the use of MCAS or Manoeuvring Characteristics Augmentation System.

This system is necessary to counteract the unique handling characteristics of this model due to it having larger more fuel efficient engines which required mounting higher up, and forward of the usual mounting point on the wing. This resulted in a change to the plane’s centre of gravity, and a slightly nose up attitude during certain flight conditions. 

The MCAS system is being heavily focused on surrounding both accidents, with early indications into the Lion Air crash pointing towards erroneous data being fed to the MCAS system due to a faulty sensor. However Boeing insists that pilots still maintain complete ability to override the MCAS system if a malfunction is suspected. 

As of 13 March, the European Union (EASA), UK, China, India, Singapore, Australia, Turkey, France, Germany, Ireland, South Korea, Mongolia, Indonesia, Malaysia, Oman, and the UAE had all implemented temporary airspace restrictions, or forced operators to ground 737 Max aircraft, as a precautionary measure. 

Additionally, airlines operating the 737 Max who have taken the decision to ground their fleet include Ethiopian Airlines, Norwegian Air, Comair, Gol Linhas Aereas, Royal Air Maroc, Aeromexico, Aerolineas Argentinas and Cayman Airways. The three largest operators of the Boeing 737 Max 8 fleet, Southwest airlines (US), Air Canada, and American Airlines continue to operate the aircraft as normal, however Southwest Airlines is offering passengers scheduled to fly on one of the Boeing planes the chance to change their bookings.

Boeing issued a statement on 12 March advising “We understand that regulatory agencies and customers have made decisions that they believe are most appropriate for their home markets. We’ll continue to engage with them to ensure they have the information needed to have confidence in operating their fleets. The United States Federal Aviation Administration is not mandating any further action at this time, and based on the information currently available, we do not have any basis to issue new guidance to operators.”


Ethiopian Airlines Flight ET302, registration ET-AVJ, departed late from Addis Ababa Bole International Airport’s runway 07R at 08:38 local time (05:38 UTC), on route for Nairobi. Minutes into the flight the crew reported a flight control problem and requested clearance to return to Addis Ababa. Air traffic control subsequently lost radar contact with the aircraft at 08:44 local time, six minutes into the flight. The flight had impacted the ground near the town of Bishoftu, 62 kilometres (39 mi) southeast of Bole International Airport. There were no survivors. 

In terms of drawing similarities with Lion Air Flight 610, there are a number of factors to examine: 

  • Both accidents involved the Boeing 737 Max 8, part of the new 737 Max range of Boeing narrow-body commercial airliners which will succeed the 737 Next Generation (NG) range.
  • The crew of both flights had requested clearance to return to the departure airport
  • Preliminary information provided by flight tracking software indicates both flights struggled to maintain a steady positive climb rate
  • Both aircraft impacted terrain in the take-off phase of the flight
  • In both accidents, weather does not appear to have played a factor with similar METeorological Aerodrome Report (METAR) conditions at both departure airports 

Despite these factors being a feature of both flights, it remains too early to conclude that any of the similarities listed support the suggestion a common crash cause. Indeed similar circumstances could be concluded in a number of previous aviation accidents where the outcome of the cause differs. 

The focus of both accidents across the media and amongst the aviation world is currently centred on the unique features of the Boeing 737 Max MCAS system. This is a new technology and was implemented on the 737 MAX to improve aircraft handling characteristics and decrease pitch-up tendency at elevated angles of attack according to Boeing. The airline manufacturer points out that MCAS does not control the airplane in normal flight; instead improving the behaviour of the airplane in a non-normal part of the operating envelope. 

But what exactly is MCAS, and why is it needed on this model of aircraft? The Boeing 737 Max is a new range of narrow body aircraft designed and produced by Boeing Commercial Airplanes as the fourth generation of the Boeing 737, succeeding the Boeing 737 Next Generation (NG). The 737 MAX series is offered in four variants; the 737 MAX 7, MAX 8, and MAX 9 will replace the 737-700, -800, and -900, respectively, and the 737 MAX 10 will be introduced as a stretched version to compete with the Airbus A321neo. Orders for the Boeing 737 MAX exceed 5000 firm orders with over 370 already delivered to airlines globally. 

As part of the requirement to introduce a more fuel efficient range, Boeing introduced larger more fuel efficient CFM International LEAP  engines, which necessitated moving the position of the engines slightly forward and up on the wing position, and also increasing the nose landing gear by eight inches. However this created a slightly upward pitching motion during certain flight conditions and to compensate Boeing introduced a computerised stabilisation system called MCAS (Manoeuvring Characteristics Augmentation System) to provide automatic trimming of the aircraft to avoid a stall scenario. 

However, as Boeing has reiterated, the system triggers only under certain, non-normal flight conditions, and these are: 

  • The AoA (angle of attack) is unusually high
  • Autopilot is disconnected
  • Flaps are up
  • The aircraft is in a steep turn. 

When the AoA is lowered, or if the pilots override the system, the MCAS is deactivated. 

The 737 MAX series gained FAA certification on March 8, 2017 with the first delivery being a MAX 8 variant on May 6, 2017 to Malindo Air.


The reaction of aviation authorities across the world, coupled with airlines electing to voluntarily ground their 737 MAX fleet, is causing considerable disruption globally. Whilst the airspace restrictions and grounding of aircraft have been described as “temporary”, no time span has been indicated and this is significant in terms of what will drive confidence in re-instating the 737 MAX operationally across the world. 

Boeing has announced it is to expedite the already scheduled series of software “enhancements” which the company claims will “make and an already safe aircraft even safer.” This is said to include updates to MCAS flight control law, pilot displays, operation manuals and crew training. Specifically the MCAS enhancement will be designed to incorporate responses to an erroneous angle of attack reading, something which is being examined as part of the Lion Air Flight 610 crash. The enhancement package is due to be completed in April 2019 according to the airline manufacturer. 

In the meantime Boeing has reiterated that the aircraft remains safe to fly given that the flight crew always retain full control over the MCAS system, with the ability to manually override the system should pilots be presented with suspicious or erroneous angle of attack (AoA) inputs. 

The airline also concludes that “Boeing’s 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018.” 

Although the Federal Aviation Administration (FAA) has not implemented any mandatory action at this time, Boeing does expect an Airworthiness Directive (AD) to be issued within the next few weeks and certainly by the end of April.  

In the meantime, the situation remains unpredictable although what would be a significant escalation in the situation is if the FAA, Boeing or North American airlines operating the 737 MAX changed their stance. It would not be the first time Boeing has grounded an entire feet; in 2013, the airline manufacturer instructed airlines not to fly their 787 Dreamliner models due to an issue with the aircrafts batteries, although this was following an FAA emergency airworthiness directive. This is a rare occurrence and the 787 grounding was the first time that the FAA had grounded an airliner type since 1979.


  • Continue to monitor the situation via Anvil updates, the media and respected aviation sources.

    • Be aware the restrictions and groundings are based on an abundance of caution and conclusions should not be drawn at this early stage. There is no current intelligence to indicate travellers should cancel flights with airlines still operating the Boeing 737 MAX, particularly given the stance taken by the FAA and the airline manufacturer. The cause of both 737 MAX accidents has not yet been determined and there is no official confirmation the aircraft was at fault.

    • If the airline you are booked with has Boeing 737 MAX aircraft as part of its fleet, and it is operating in one of the countries which have restricted airspace, expect ongoing disruption and even cancellations. Check with your airline to confirm this information.

    • In the majority of cases, airlines will switch out 737 MAX aircraft with other model variants. However this could also result in reduced passenger capacity and overbooking issues, which may mean some passengers are moved onto later flights.

    • The level of disruption is not expected to cause major disruption at this time; particularly given March is an-off peak month for tourist air travel. This could change if the situation continues into the spring, particularly as several airlines are expecting delivery of 737 MAX aircraft to implement into busy route scheduling operations.

    • You should check your rights in terms of your flight being cancelled or delayed. European air passengers’ rights rules will apply and passengers must be provided for, however due to the fact this grounding will count as a “hidden manufacturing defect” there is no requirement for the airlines to pay compensation.