Maintenance records for most of Alaska Airlines’ fleet are being reviewed after federal inspectors found two planes were returned to service prematurely. Company officials agreed to make the review because of incomplete paperwork discovered by the Federal Aviation Administration during an inspection of maintenance operations in Seattle, Oakland, Calif., and elsewhere. One plane was released for service in Seattle without a required second signature on some maintenance paperwork. The 737, which was carrying passengers when the discrepancy was revealed, was stopped in Los Angeles for an inspection but no problems were found, Alaska spokesman Greg Witter said. On the second aircraft, an MD-80, inspectors could not determine whether certain work had been done, FAA spokesman Paul Turk said.