Summaries of FBI interviews with flight instructors show that the pilot who deliberately flew his airliner into a mountainside last year had struggled with learning to fly. He had failed a key test of his flying skills during his U.S. training but was promoted anyway.

Attorneys representing families of crash victims say pilot Andreas Lubitz's training difficulties were one more "red flag" that should have caused Lufthansa and the airline's Arizona flight school to take a closer look at him and discover his history of depression.

The FBI conducted the interviews a week after the crash. Attorneys said they were only recently provided the summaries by prosecutors in Germany. The lawyers provided copies to The Associated Press.

Lufthansa and flight school officials didn't immediately respond to requests for comment.