It has been reported that wing flaps on the Spanair jet that crashed in Spain last month killing 154 people were not fully extended before take-off.
A report in the Wall Street Journal has said preliminary information from the MD-82's flight data recorder shows the flaps which provide extra lift were not properly positioned.
According to the paper, information from the data recorder also indicates that both engines were working properly and there was no fire before impact into a ravine at the edge of the Madrid airport runway.
But the paper also said investigators wanted to know why a loud horn designed to alert the crew to equipment problems apparently did not sound.
They were also checking why the unextended flaps apparently were not noticed during the pilots' routine pre-departure equipment check.
The 20 August accident was Spain's worst air crash in 25 years. 18 people survived.
Investigators were not expected to reach conclusions for some time, and the probe could still yield other results.
The MD-80 family is manufactured by McDonnell Douglas, which is now part of Boeing Co.
Spanair is owned by Scandinavia's SAS.
