Boeing has raised concern over the design of a jet made by its European rival Airbus.
The model in question the extra-long range version of its newest plane, the A321neo.
Boeing says it could pose a fire risk due to its fuel tank.
In a submission to European regulators, Boeing said the design of the fuel tank intended to increase the plane's range posed many potential hazards.
In most jets, fuel is carried in wings and central tanks, but to meet demand for longer routes Airbus plans to mold a tank directly into the fuselage.
Its shape would follow the contours of the jet and carry more fuel.
The design is crucial to the A321XLR's main marketing ploy - to be the longest range of any single-aisle jet - and is due for release in 2023.
Boeing's intervention is not unusual in a global system which regularly allows manufacturers to chime in when safety rules are being interpreted.
But the timing is pivotal.
The U.S. plane giant is trying to repair its image following the crisis over its 737 MAX.
That plane model was grounded for almost two years following two deadly crashes.
The airline industry, which has been battered by the global health crisis, is now facing tougher scrutiny.
While insisting they never compete on safety, Airbus and Boeing have a record of goading each other on technical issues.