American Airlines MD-80 aircraft sit on the tarmac at the Dallas Fort Worth International Airport.
The newspaper on Saturday reported that at least one of the Fort Worth-based airline's McDonnell Douglas MD-80 series jets is believed to be in such poor shape that it was ferried without passengers to a maintenance base at low altitudes to avoid stressing the fuselage by pressurizing it. The paper cited unnamed people familiar with the matter.
Attempts by The Associated Press to reach American Airlines officials by phone or by e-mail Saturday were not successful.
But American Airlines spokesman Tim Wagner told the Wall Street Journal that the carrier has responded to the FAA's formal "letter of investigation."
Wagner also told the Journal that any actions or precautions taken earlier this year "whether airplane movements or repairs, were done with the highest level of safety in mind."