A LEAR 35 FLC WAS RECLRED TO AN ALT THEN DIRECTED TO DSND TO THE PREVIOUS ALT BY ZLA.

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IT WAS A NORMAL DAY; VISIBILITY WAS MORE THAN 10 MI AND CLR. AFTER DEPARTING LAX ON AN IFR PART 91 FLT; JUST RETURNING INTO SVC FROM MAINT; WE WERE CLRED ON RWY HDG (RWY 25R) TO MAINTAIN 2000 FT AND THEN CLRED TO 3000 FT BEFORE REACHING 2000 FT. ATC THEN CLRED US TO 10000 FT WITH TFC AT OUR 1 O'CLOCK POS OFF THE N RWYS; LOOKED TO BE A B757. AFTER PASSING SOMEWHERE THROUGH 5500 FT; ATC ASKED US TO MAINTAIN 9000 FT. RADIO COMS AT THE TIME WERE MODERATE AND SOMETIME VERY SOON SOCAL ASKED US TO CONTACT ZLA ON FREQ 135.50. AFTER WE LEVELED OFF WE WERE THEN CLRED TO 10000 FT AND LEVELED OFF THERE. ATC THEN CLRED US DIRECT VTU DIRECT KWANG INTXN AND MAINTAIN 11000 FT; AT WHICH TIME MY COPLT READ BACK; 'CLRED DIRECT VTU DIRECT KWANG 11000 FT.' AFTER REACHING 11000 FT; ATC CALLED; ACFT X SAY ALT. MY COPLT RESPONDED; LEVEL 11000 FT. ATC THEN RESPONDED BACK AND SAID WE WERE CLRED TO MAINTAIN 10000 FT; DSND IMMEDIATELY TO 10000 FT. WE IMMEDIATELY DSNDED TO 10000 FT. NOTHING FURTHER WAS DISCUSSED BY ATC REGARDING THIS APPARENT DEV. NO OTHER MEASURES WERE TAKEN BY US OR ANY OTHER ACFT TO MY KNOWLEDGE. MY COPLT AND I BOTH HEARD OUR CLRNC TO MAINTAIN 11000 FT WITH A READBACK AND BOTH FELT VERY CONFIDENT THAT WE HEARD THE CLRNC CORRECTLY.