CUDAHY, CA (AP) — Federal authorities will investigate why an airliner with engine trouble dumped jet fuel over a densely populated area of Southern California while making an emergency return, dousing dozens of schoolchildren in a smelly vapor. Delta Air Lines Flight 89 to Shanghai turned back to Los Angeles International Airport only minutes after taking off Tuesday. The pilot reported a stalled engine compressor, which can reduce thrust. The Federal Aviation Administration says it will investigate. The agency says procedures call for fuel-dumping over unpopulated areas. But an aerospace consultant says the pilot can deviate from those rules for safety reasons.