The issue involves a potential manufacturing quality problem with low-pressure turbine discs in the CFM LEAP 1B engine, Boeing said.
CFM, a joint venture between General Electric Aviation and French aerospace company Safran, is making the new engine model for what is already Boeing's fastest-selling aircraft.
Chicago-based Boeing (NYSE: BA) said its flights have not had any engine problems, but that it halted the flights "out of an abundance of caution" and is working with engine maker CFM to determine the root of the problem.
"The step is consistent with our priority focus on safety for all who use and fly our products," Boeing said.
Boeing said it still plans to begin 737 Max deliveries this month. All Boeing 737 aircraft are made at Boeing Commercial Airplanes' sprawling Renton complex. Production of the Max aircraft and the older Next Generation 737 aircraft will continue.
Until now, the development of the fuel-efficient airplane and its flight tests have gone off without a hitch.
Boeing reiterated its confidence in the engine, saying "the LEAP 1B and 737 Max have been certified to the most stringent requirements in commercial aviation."
The U.S. Federal Aviation Administration (FAA) certified Boeing's new 737 Max 8 airplane for passenger airline service in March after more than a year of intensive tests.
Boeing recently launched more flight and certification tests for its larger 737 Max 9, a longer version that has more seats than than Max 8.
Here is the complete text of Boeing's statement, issued this morning:
"CFM has notified us of a potential manufacturing quality escape with low pressure turbine (LPT) discs in LEAP 1B engines delivered to Boeing."
"We are working with CFM to inspect the discs in question. CFM and its supplier notified us after discovering the issue as a part of their quality inspection process. At no time have we experienced an issue associated with the LPT during our ongoing Max testing program."
"Out of an abundance of caution, we decided to temporarily suspend Max flights. The step is consistent with our priority focus on safety for all who use and fly our products."
"The Max 8 flight test program put over 2000 hours on the engines, including abuse testing and flights lasting over 9 hours, undergoing thorough inspections throughout. Additionally, 180-minute ETOPS testing completed in April, 2017 required another 3,000 simulated flight cycles on the test stand, before a complete inspection was conducted by CFM. The LEAP 1B and 737 Max have been certified to the most stringent requirements in commercial aviation."
"We will work closely with CFM to understand the precise scope and root cause of the quality issue."
"Our plan remains to begin Max deliveries in May. Max production will continue, as will production and delivery of our Next-Generation 737 airplanes."
(Andrew McIntosh - Puget Sound Business Journal)