After the Civil Aviation Authority (CAA) grounded the Boeing 737 MAX plane involved in two fatal crashes, tens of thousands of passengers will be affected.
These are the key questions and answers.
Why are there concerns over this aircraft type?
On 10 March 2019, all 157 passengers and crew aboard an Ethiopian Airlines Boeing 737 MAX 8 died when it crashed shortly after take-off from Addis Ababa on a routine flight to Nairobi.
It was the second fatal accident involving what is a very modern aircraft. Fluctuations in the vertical speed of the aircraft show some similarities with the performance of a Lion Air 737 MAX 8 which crashed shortly after take off from Jakarta airport in October 2018, with the loss of 189 lives.
Concern has centred on some software installed to protect against a stall. Evidence from the Indonesian crash implicates this safety measure in the fatal accident.
Why has the UK banned the aircraft now?
It follows grounding orders issued by China, South Korea, Indonesia, Malaysia, Singapore and Australia. The CAA does not feel it has “sufficient information from the flight data recorder” of the Ethiopian Airline aircraft.
“We have, as a precautionary measure, issued instructions to stop any commercial passenger flights from any operator arriving, departing or overflying UK airspace,” said a spokesperson.
Which airlines – and passengers – will it affect?
Tui Airways has five of the aircraft based in the UK, mainly in Manchester, and uses them on a wide range of longer European and North African links – on the day of the ban aircraft were in the sky on flights linking Manchester with Alicante and Marrakech.
The airline said: “Tui Airways can confirm that all 737 MAX 8 aircraft currently operating in the UK have been grounded following the decision from the UK regulatory authorities today.
“Any customers due to fly home today on a 737 MAX 8 from their holiday will be flown back on another aircraft.
“Customers due to travel in the coming days will also travel on holiday as planned on other aircraft. The safety and wellbeing of our customers and staff has remained our primary concern.”
Norwegian Air has 18 Boeing 737 MAX 8 aircraft and has said it will ground the entire fleet, even though many of them could avoid UK airspace. The carrier has 110 Boeing 737-800 aircraft, which are unaffected by the ban.
The airline said: “We are now working on re-allocating our fleet options with other aircraft types, re-bookings to other flights and combining flights to minimise inconvenience caused for our passengers.
“We would like to apologise to customers who are affected, but the safety and security of our customers and colleagues will never be compromised. Affected passengers will be informed via SMS and our web pages.”
Is there likely to be disruption?
Initially some thousands of passengers will find themselves unable to reach their intended destination, as other aircraft are sought to operate the flights.
Over the next three weeks there is likely to be a modest amount of disruption due to a significant slice of airlines’ fleets being grounded. The Independent has asked Tui Airways and Norwegian for guidance on what they should expect.
March is an off-peak month, but once Easter and the main summer season begins the absence of these aircraft will be more seriously felt.
In particular, Ryanair – the biggest European customer for the jet – is expecting to start flying the plane in May, on a busy network from Stansted.
Airlines will seek to minimise disruption by sub-chartering capacity, using larger aircraft or keeping older planes flying beyond their intended replacement date.
What are my rights if my flight is delayed or cancelled?
European air passengers’ rights rules will apply. There is no compensation payable, because this grounding will count as a “hidden manufacturing defect”. But airlines must provide alternative flights and, if a wait is involved, source hotels and provide meals for disrupted passengers.
What is the technical background?
Boeing’s stall-protection measure is designed to respond when the angle-of-attack sensor indicates danger.
The system works by measuring the “angle of attack” – the angle between the wing and the airflow. If it increases beyond a certain point, then the lift produced by the wings is insufficient to keep the aircraft flying.
It will automatically nudge the nose downwards, by operating an elevator in the tail, even if the pilots are flying manually rather than on autopilot.
The pilots are then expected to take action to address the potential stall issue.
But an Emergency Airworthiness Directive issued by the Federal Aviation Administration (FAA) shortly after the Lion Air crash warned: “If an erroneously high single angle of attack sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer.
“This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.”
The directive ordered airlines to advise pilots about how to deal with the phenomenon should it arise.
The FAA said the issue “is likely to exist or develop in other products of the same type design”.
Many pilots have expressed concern that Boeing had failed to communicate what they see as a very significant change to the way the 737 flies.