<PAGE>   1
                                                                       EXHBIT 12


                              IRIDIUM OPERATING LLC

                   (A WHOLLY-OWNED SUBSIDIARY OF IRIDIUM LLC)
                 (A DEVELOPMENT STAGE LIMITED LIABILITY COMPANY)
               COMPUTATION OF RATIOS OF EARNINGS TO FIXED CHARGES
                                ($ IN THOUSANDS)

<TABLE>
<CAPTION>

                                                                                     PERIODS FOLLOWING INITIAL
                                                                                     CAPITAL CONTRIBUTION DATE


                                              YEAR ENDED     JANUARY 1, 1993     JULY 29, 1993 TO         DECEMBER 31,
                                              DECEMBER 31,   TO JULY 30, 1993      DECEMBER 31
                                                  1992                                1993             1994        1995
<S>                                          <C>              <C>                <C>             <C>          <C>     
Fixed charges:
  Capitalized Interest...................            --               --                 --               --          --
  Portion of rent expense
    representative of interest (1).......            --               --                 54              264         342
                                               --------         --------           --------         --------     -------

            Total fixed charges..........            --               --                 54              264         342
                                               ========         ========           ========         ========     =======

Earnings:
  Loss before income taxes...............        (8,773)          (5,309)            (6,751)         (13,309)    (21,961)
  Fixed charges, less capitalized
    interest.............................            --               --                 54              264         342
                                               --------         --------           --------         ---------    -------
  Earnings adjusted for fixed
    charges..............................        (8,773)          (5,309)            (6,697)         (13,045)    (21,619)
                                                =======          =======           ========          ========    =======

Ratio of earnings to fixed
  charges................................            --               --                 --               --          --
Deficiency in earnings to cover
  fixed charges..........................         8,773            5,309              6,751           13,309      21,961
</TABLE>



<TABLE>
<CAPTION>
                                                         PERIODS FOLLOWING INITIAL
                                                         CAPITAL CONTRIBUTION DATE
                                                               DECEMBER 31,
                                                   1996           1997            1998
<S>                                          <C>             <C>             <C>           
Fixed charges:
  Interest expense.......................              --             --         273,219
  Capitalized Interest...................          28,127        163,747         170,089
  Portion of rent expense
    representative of interest (1).......             398          3,858           5,421
                                                ---------        -------         -------

            Total fixed charges..........          28,525        167,605         448,729
                                                =========        =======         =======

Earnings:
  Loss before income taxes...............         (69,009)      (293,401)     (1,252,509)
  Fixed charges, less capitalized
    interest.............................             398          3,858         278,640
  Amortization of capitalized 
    interest.............................              --          7,900          36,795
                                                ---------      ---------       ---------
  Earnings adjusted for fixed
    charges..............................         (68,611)      (281,643)       (937,074)
                                                =========      =========       =========

Ratio of earnings to fixed
  charges................................              --             --              --
Deficiency in earnings to cover
  fixed charges..........................          97,136        449,248       1,385,803
</TABLE>