Engines manufactured by Pratt & Whitney for the latest Airbus A320neo single-aisle jetliner pose a shutdown risk, the U.S. aviation regulator warns. The warning comes after European regulators raised their concerns about potential inflight shutdown and rejected takeoffs.

The Federal Aviation Association (FAA) warning, issued on February 14, 2018, cites a “knife edge seal failure” in the engine that could lead to an engine stall “and consequent inflight shutdown and rejected takeoffs,” the agency said in an airworthiness directive (AD).*

The warning is the latest in a series of issues that have emerged as Pratt & Whitney, a unit of U.S. United Technologies, rolled out its new fuel-efficient geared turbofan (GTF) engines.

These engines compete with the market-leader CFM International, a joint venture between GE Aviation – a division of the U.S. General Electrics – and Safran Aircraft Engines – a division of France’s Safran.

The FAA’s warning comes after a similar action by European Aviation Safety Agency (EASA) on February 9, 2018. The agency issued an emergency airworthiness directive (AD) for Airbus A320 and A321 (the A320-271N, A321-271N, A321-272N) aircraft indicating that several occurrences of engine in-flight shutdown (IFSD) and rejected take-off (RTO) have been reported on these Airbus A320neo-family planes.

A total of 98 engines could be affected, with 43 confirmed to have the problem and the rest possibly affected, Pratt & Whitney told Reuters.

The company has not halted production or delivery of the engines and plans to submit a proposal to the EASA on February 16, 2018, detailing how to fix the problems. It is not clear how long it will take for the European regulator to approve the plan.

The problem supposedly affects only the PW1100 series engines and not the similar engines for Bombardier CSeries, Embraer’s second-generation E-Jets or Mitsubishi Regional Jet. Aircraft using alternative engines from CFM International are also not affected, Reuters reports.

Nevertheless, both Airbus and Bombardier have blamed the company for A320neo-family and CSeries aircraft delivery delays as the engine provider struggled to speed up production with simultaneously introduced fixes addressing reliability and durability shortfalls, ATW writes.

On February 10, 2018, news emerged that Airbus halted deliveries of its A320neo jets powered by Pratt & Whitney GTF engines and halted pre-delivery test flights.

By February 12, 2018, Airbus had grounded 11 of the 113 Pratt & Whitney-powered A320neos currently in service, with the 43 in-service engines affected. As a result, the European plane maker’s shares fell significantly.

Now industry sources say that 20 A320neo jets were grounded by airlines, including India’s largest carrier, IndiGo.

Pratt & Whitney is one of two engine suppliers for the best-selling A320neo-family aircraft, the other being its rival CFM International.

*Airworthiness Directives are legally enforceable regulations issued by the FAA to address an unsafe condition in an aircraft, engine, propeller, or appliance.