WASHINGTON, March 12 -- The U.S. Federal Aviation Administration (FAA) had warned of a "cracking" problem on Boeing 777 airplanes, just days before the Malaysia Airlines Flight MH370 went missing.

However, the FAA "airworthiness directive (AD)," dated March 5, only applied to B777-200, -200LR, -300, -300ER, and -777F series airplanes, not the B777-200ER, which is the model of the missing MH370.

The FAA cautioned against a link between the directive and the accident, and Laura Brown, the aviation regulator's deputy assistant administrator for public affairs, told Xinhua Wednesday "this applies only to U.S. registered aircraft."

"The civil aviation authorities in other countries usually issue identical or similar directives that apply to aircraft registered in their countries," Brown added.

The FAA said the directive was prompted by a report of cracking in the fuselage skin underneath the satellite communication (SATCOM) antenna adapter.

"We are issuing this AD to detect and correct cracking and corrosion in the fuselage skin, which could lead to rapid decompression and loss of structural integrity of the airplane," the U.S. aviation regulator said.

"This AD requires repetitive inspections of the visible fuselage skin and doubler if installed, for cracking, corrosion, and any indication of contact of a certain fastener to a bonding jumper, and repair if necessary," it said.

The directive, first drawn up on September 26, 2013, was approved on February 18 and published in the U.S. Federal Register on March 5. It's due to take effect on April 9.

In the notice, the FAA said one operator had reported a 16-inch (40.6-centimeter) crack under the 3-bay SATCOM antenna adapter plate in the crown skin of the fuselage on an airplane that was 14 years old with approximately 14,000 total flight cycles.

It said following the crack finding, the same operator inspected 42 other airplanes that are between 6 and 16 years old and "found some local corrosion, but no other cracking."

The FAA said 120 airplanes of U.S. registry are affected by the directive.

The international search for missing flight MH370 entered its fifth day Wednesday, and multinational search operations for the missing plane has extended to land. But the whereabouts of the airplane remains unknown.