( CNN ) -- The Marine Corps has sacked four top officers of a California-based fighter squadron over the December crash of a fighter jet that slammed into a San Diego neighborhood , the service announced Tuesday . Grace Yoon , 15 months , was killed after a military jet crashed into her home . Deferred maintenance and faulty decisions by the pilot and squadron members with whom he was communicating on the ground contributed to the crash , a Marine Corps investigation concluded . The commander of the squadron involved , its top maintenance officer and two others have been relieved of duty as a result of the investigation , and nine other Marines have received other disciplinary action , Maj. Gen. Randolph Alles said . The jet crashed in the University City neighborhood of San Diego , about three miles short of the Miramar airfield . Two adults and two small children from a Korean immigrant family were killed when the jet slammed into their house . Watch what pilot said as plane had trouble » . The F/A-18 Hornet crashed after `` a succession of emergencies '' that began with oil-pressure problems in its right engine during a flight off the Southern California coast , said Marine Col. John Rupp . That left the jet relying on its other engine , which previously had been giving mechanics electronic indications of a problem with its fuel-flow system , Rupp said . Learn more about the jet » . Maintenance rules do n't require immediate repairs for the problem , he said , but the squadron flew the jet 146 times before it eventually crashed because its left engine was starved for fuel . `` The end result was that the squadron elected to fly an aircraft that had a degraded fuel system on the left side of the aircraft , '' Rupp said . `` This is a critical point , and this was collectively questionable judgment on the part of the squadron 's maintenance department . '' The investigation criticized the pilot , who was being trained on the F/A-18 , for not consulting a pocket checklist that outlined emergency procedures . While controllers aboard the aircraft carrier that launched the jet urged the pilot to land at a nearby Navy airfield at North Island , squadron officers relied on `` incorrect assumptions and inaccurate data '' to guide him back to the plane 's base at the Miramar Marine Corps Air Station . `` No one in the ready room stated or understood the severity of the low fuel emergency at this time , '' Rupp said . `` This is a critical moment , and this is collectively bad decision-making by the duty officer , by the operations officer and by the squadron 's commanding officer . '' The pilot waited `` until the last possible moment '' to eject from the plane , bailing out at an altitude of just 400 feet , and attempted to steer away from homes on the ground before the crash , Rupp said . The pilot , whose name has not been released , is grounded pending further review , which Marine officers said was routine . Alles said the officer was an `` above-average '' pilot who `` just made a poor decision . '' Dong Yun Yoon lost his wife , children and mother-in-law in the crash and another unoccupied house also was destroyed . Yoon said the victims were his daughter Rachel , who was born less than two months before the accident ; his 15-month-old daughter Grace ; his wife , Young Mi Yoon , 36 ; and her 60-year-old mother , Suk Im Kim , who he said had come to the United States from Korea recently to help take care of the children . In an emotional press conference in December , Yoon said he did not blame the pilot and urged the public to pray for him . `` I do n't blame him . I do n't have any hard feelings . I know he did everything he could , '' Yoon said at the time . `` Please pray for him not to suffer from this accident , '' Yoon said as he fought for composure . `` He is one of our treasures for the country . ''
NEW : ` ` reports of emergencies '' with aircraft preceded fatal San Diego crash . NEW : Squadron officers rely on ` ` inaccurate signals '' to direct pilot to return to base . NEW : Pilot criticized for not consulting pocket checklist of emergency procedures . Pilot 's wife , children , mother - in - law all were killed in crash .