ALLEGED ALTDEV ON SID DEP PROC WHEN RTING IS ALTERED AND ALT AMENDED.

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AT AM00 LCL; FLT PUSHED FROM GATE AT ONTARIO INTL ARPT BOUND FOR LAS VEGAS. AFTER CONTACTING THE TWR HE TOLD US TO TAXI DOWN RWY 8L AND HOLD IN POS. WHILE WE HELD IN POS 2 ACFT DEPARTED RWY 8R. AN ACR PLANE TOOK OFF AND TWR TOLD HIM TO MAINTAIN 3000. THEN A PROP PLANE TOOK OFF. AFTER THE PROP PLANE DEPARTED WE WERE CLRED FOR TKOF. I ASKED THE TWR IF HE WANTED US TO MAINTAIN 3000. HE SAID; 'NO THAT WAS FOR ANOTHER ACFT; MAINTAIN 14000.' WE TOOK OFF AT AM17 LCL. AFTER CLBING AND PASSING 500 AGL WE STARTED OUR TURN TO 255 DEGS. DURING THE TURN TWR HANDED US TO DEP 125.5. UPON MAKING CONTACT; HE CLRED US 'DIRECT POMONA; DAGGETT TRANSITION.' THIS NEW CLRNC SEEMED TO REINFORCE THE NEW ALT WHICH IS ON THE DAGGETT TRANSITION. SOMETIME PRIOR TO POMONA; DEP HANDED US TO LOS ANGELES CENTER. AT THAT TIME LAX ASKED US IF WE HAD A XING RESTRICTION OVER POMONA. MY FO AND I BOTH UNDERSTOOD THAT WE WERE CLRED TO 14000 FT ON THE DAGGETT TRANSITION. LAX CENTER INSTRUCTED US TO MAINTAIN PRESENT ALT WHICH WAS 9000. LATER HE TOLD US TO CLB ON COURSE. STILL LATER ON THAT FREQ; LAX REQUESTED US TO CALL THEM OVER THE TELEPHONE. AFTER WE LANDED IN LAS VEGAS; I CALLED BOTH LAX CENTER AND ONTARIO TRACON. THE SITUATION COULD EASILY HAVE BEEN PREVENTED WITH AN INSERTION IN THE CLRNC FROM ONTARIO DEP; 'CLRED DIRECT POMONA; DAGGETT TRANSITION; MAINTAIN 8000.' I ALSO SHOULD HAVE VERIFIED THE CLRNC WITH A SPECIFIC REF TO THE ALT BUT THE FREQ WAS A LITTLE BUSY. NEXT TIME I'LL LET HIM KNOW WHAT I PLAN TO DO. SUPPLEMENTAL INFO FROM ACN 193144: WE ARE NOW USING A DIFFERENT RWY FOR DEP AND HOLDING IN POS; AWAITING DEPS OFF OF 8R. WE ASK THE TWR IF THE 3000 WAS FOR US AND TWR SAID NO; THAT'S FOR ANOTHER ACFT; MAINTAIN 14000. NOTE: TKOF IS NOW ON 8L; ORIGINAL CLRNC AND DEP PREDICATED ON 8R. MAINTAIN 14000. NEWLY ASSIGNED ALT; DELETES ALL OTHERS; FARS. UNRESTRICTED TO 14000 AT THIS TIME. CONTACTED DEP; 125.5 DEP; RADAR CONTACT; PROCEED DIRECT TO POM. WE ARE NOW GOING DIRECT TO POM. WE ARE NOW TAKEN OFF OF THE SID; (255 HDG; INTERCEPT THE POM 114R). THIS DIRECT CLRNC TO POM FURTHER REINFORCES OUR THOUGHTS OF UNRESTRICTED CLB TO 14000. AS USUAL; GREAT WORK BTWN TWR AND DEP TO EXPEDITE TFC; DUE TO THE DELAYS. DEP CLRED US DIRECT POM. HE IS WATCHING THE DEP GATE AND CLB. IF THE CTLR SAW A POTENTIAL ALT PROBLEM COMING UP; WHY DID HE NOT ADVISE AS WE WERE FAST APCHING THE 8000 FT LEVEL? A SUGGESTION THAT MAY HELP PREVENT ALT CONFLICTS IN THE FUTURE: WHEN CLRNC DELIVERY IS ISSUING A CLRNC; THE FIRST ALT RESTRICTION ON THE SID SHOULD BE THE ALT TO MAINTAIN; NOT AN ALT AFTER THE FIRST RESTRICTION. THIS INFO PASSED TO THE TWR.