Exhibit 99.1

    [GRAPHIC OMITTED]

    Overview of Improved Transaction Economics

    July 2009

    GHL Acquisition Corp.

    slide01

    [GRAPHIC OMITTED]
    Forward Looking Statements
    --------------------------------------------------------------------------------

    This communication contains forward-looking statements within the meaning of
    Section 27A of the Securities Act of 1933, as amended, and Section 21E of the
    Securities Exchange Act of 1934, as amended. The words "anticipates", "may",
    "can", "believes", "expects", "projects",

    "intends", "likely", "will", "to be" and other expressions that are predictions
    of or indicate future events, trends or prospects and which do not relate to
    historical matters identify forward-looking statements. These forward-looking
    statements involve known and unknown risks, uncertainties and other factors
    that may cause the actual results, performance or achievements of GHL
    Acquisition Corp. ("GHQ") and/or Iridium Holdings LLC ("Iridium") to differ
    materially from any future results, performance or achievements expressed or
    implied by such forward-looking statements. All statements other than
    statements of historical fact are statements that could be deemed
    forward-looking statements. These risks and uncertainties include, but are not
    limited to, uncertainties regarding the timing of the proposed transaction with
    Iridium, whether the transaction will be approved by GHQ's stockholders,
    whether the closing conditions will be satisfied (including receipt of
    regulatory approvals), as well as industry and economic conditions,
    competitive, legal, governmental and technological factors. There is no
    assurance that GHQ's or Iridium's expectations will be realized. If one or more
    of these risks or uncertainties materialize, or if our underlying assumptions
    prove incorrect, actual results may vary materially from those expected,
    estimated or projected. Readers are cautioned not to place undue reliance on
    these forward-looking statements, which speak only as of the date hereof.
    Except for our ongoing obligations to disclose material information under the
    Federal securities laws, we undertake no obligation to release publicly any
    revisions to any forward-looking statements, to report events or to report the
    occurrence of unanticipated events.

                                                                                   2

    [GRAPHIC OMITTED]
    slide02

    [GRAPHIC OMITTED]
    Additional Information and Where to Find It
    --------------------------------------------------------------------------------

    This communication is being made with respect to a proposed acquisition and
    related transactions involving GHQ and Iridium. In connection with these
    proposed transactions,

    GHQ has filed with the Securities Exchange Commission ("SEC") a preliminary
    proxy statement and intends to mail a definitive proxy statement and other
    relevant documents to GHQ's stockholders. The information contained in this
    communication is not complete and may be changed. Before making any voting or
    investment decisions, GHQ's stockholders and other interested persons are urged
    to read GHQ's preliminary proxy statement, and any amendments thereto, and the
    definitive proxy statement in connection with GHQ's solicitation of proxies for
    the special meeting to be held to approve the acquisition and any other
    relevant documents filed with the SEC because they will contain important
    information about Iridium, GHQ and the proposed transactions. The definitive
    proxy statement will be mailed to GHQ stockholders as of a record date to be
    established for voting on the proposed acquisition. Stockholders and other
    interested persons will also be able to obtain a copy of the preliminary and
    definitive proxy statements once they are available, without charge, at the
    SEC's web site at http://www.sec.gov or by directing a request to: GHL
    Acquisition

    Corp., 300 Park Avenue, 23rd Floor, New York, New York,
    telephone: (212) 372-4180.

                                                                                   3
    [GRAPHIC OMITTED]
    slide03

    [GRAPHIC OMITTED]

    Participants in the Solicitation
    --------------------------------------------------------------------------------
    GHQ and its directors and officers may be deemed to be participants in the
    solicitation of proxies to GHQ's stockholders in connection with the
    acquisition. A list of the names of those directors and officers and a
    description of their interests in GHQ is contained in GHQ's report on Form 10-K
    for the fiscal year ended December 31, 2008, which is filed with the SEC, and
    will also be contained in GHQ's proxy statement when it becomes available.
    GHQ's stockholders may obtain additional information about the direct and
    indirect interests of the participants in the acquisition, by security holdings
    or otherwise, by reading GHQ's proxy statement and other materials to be filed
    with the SEC as such information becomes available.

    Nothing in this communication should be construed as, or is intended to be, a
    solicitation for or an offer to provide investment advisory services.

                                                                                   4
    [GRAPHIC OMITTED]
    slide04

                                            Steps Taken in Preparation for Merger
                                            Vote
                                            Improving Transaction Economics and
                                            Facilitating Stockholder Approval

    --------------------------------------  ----------------------------------------
    GHQ and Iridium have in recent months   [] Transaction Price Reduction
    taken a number of steps which both         Announced in Late-April
    facilitate the closing of the proposed
    merger and increase the attractiveness     > 15% reduction in consideration to
    of the pro- forma company valuation          be paid to existing Iridium holders

    Today's warrant restructuring              > Strong equity market performance
    announcement further improves the          since then (S&P 500 up 15%; Inmarsat
    economics of the merger for GHQ            up 13%)
    stockholders
                                            [] Elimination of ~3.7 Million GHQ
                                               Warrants Held by Bank of America

                                               > Will be repurchased upon merger
                                                 closing for $0.50 each

                                            [] GHQ Warrant Restructuring Announced
                                               Today

                                               > Meaningfully reduces warrant
                                                 overhang on GHQ shares post-closing

                                               > Reduces pro-forma,
                                                 fully-distributed EBITDA multiple

                                               > ~14.4 million warrants will have
                                                 their strike price raised and
                                                 expiration date extended and ~12.4
                                                 million additional warrants will be
                                                 exchanged for GHQ shares and cash

                                                                                   5
    [GRAPHIC OMITTED]
    slide05

                                            Details of Warrant Restructuring
    --------------------------------------  ----------------------------------------
    As a result of the warrant              [] In total, ~30.5 million GHQ warrant
    restructuring, GHQ will have               will be repurchased or restructured
    dramatically fewer in-the-money            upon closing of the acquisition of
    warrants outstanding upon closing of       Iridium
    the Iridium merger, which is
    expected to improve share trading          > Represents ~69% of the 44.1 million
    dynamics and enhance the pro-forma           warrants that would otherwise have
    valuation for stockholders                   been outstanding following the
                                                 acquisition

                                               > Reduces pro-forma, fully-
                                                 distributed EBITDA multiple and
                                                 diminishes warrant overhang on GHQ
                                                 shares

                                               > Repurchases conducted at
                                                 meaningful discount to intrinsic
                                                 value assuming Iridium closing;
                                                 restructurings significantly raise
                                                 strike prices to out-of-the-money
                                                 levels

                                            [] Repurchase of ~3.7 million warrants
                                               held by Bank of America (previously
                                               announced)

                                               > Purchase price of $0.50 each or
                                                 ~$1.8 million in aggregate

                                            [] Restructuring of ~14.4 million
                                               warrants held by various holders

                                               > Strike price increased to 15%
                                                 above share offering price in a
                                                 future GHQ common equity offering
                                                 (subject to a maximum strike price
                                                 of $11.50)

                                               > Expiration date extended by two
                                                 years to February 2015

                                               > Includes all of the 4.0 million
                                                 remaining private placement warrant
                                                 held by Greenhill and 0.4 million
                                                 warrants held by executives of GHL
                                                 Acquisition

                                            [] Repurchase of ~12.4 million warrant
                                               held by various holders

                                               > Aggregate purchase price of ~$3.1
                                                 million of cash and ~$12.4 million
                                                 of GHQ common stock with the number
                                                 of shares based on the offering
                                                 price in a future GHQ common equity
                                                 offering (subject to minimum of
                                                 one-tenth of a share per warrant)

                                            [] Greenhill will own the following
                                               securities post-closing of the
                                               acquisition of Iridium

                                               > ~6.9 million GHQ common shares,
                                                 which it received for founding GHQ
                                                 and making an $8 million initial
                                                 equity investment

                                               > ~1.9 million GHQ common shares,
                                                 resulting from conversion of its
                                                 $22.9 million convertible note
                                                 investment in Iridium

                                               > 4.0 million GHQ warrants with an
                                                 out-of-the-money strike price as
                                                 described above

                                                                                   6

    [GRAPHIC OMITTED]
    slide06

                                            Summary of Post-Transaction Iridium
                                            Balance Sheet

                                            Including Effects of Warrant
                                            Restructuring; Assuming 30%
                                            Redemptions
    --------------------------------------  ----------------------------------------
    Post-merger, Iridium will have a        (All Values in Millions)          1/2009
    strong balance sheet with minimal                                     Proo Forma
    leverage                                Unrestricted Cash (1)(3)          $150.1
                                            Other Current Assets                83.3
                                            Property & Equipment, Net          411.8
                                            Other Long-Term Assets              23.6
                                            Goodwill & Intangibles             130.4
                                                                              ------
                                                                              ------
                                            Total Assets                      $799.2
                                                                              ------
                                            Current Liabilities (1)
                                                                              ------
                                                                               $83.2
                                            Motorola Payable                    10.4
                                            Debt (Short-Term & Long-Term) (2)   46.7
                                            Other Liabilities                   84.6
                                                                              ------
                                            Total Liabilities                  224.9
                                            Stockholders' Equity (2)           574.3
                                                                              ------
                                                                              ------
                                            Total Liabilities & Stockholders'
                                              Equity                          $799.2
                                                                              ------
                                            Notes:
                                                                              ------

                                             Net Cash (3)                      $93.0
                                             Fully-Diluted Shares
                                               Outstanding (3)(4)             71.791
                                             Future Potential Warrant
                                               Proceeds (5)                   $260.8

                                            Source: GHQ Schedule 14A filed 6/8/09,
                                            adjusted for warrant restructuring and
                                            other items below.

                                            (1) Stated prior to payment of $25.5
                                            million tax step-up payment, due
                                            90-days post-closing.

                                            (2) Assumes conversion of Greenhill
                                            convertible note into equity.

                                            (3) Assumes 30% of GHQ's existing
                                            public stockholders elect conversion
                                            for $10.00 in cash per share. Motorola
                                            Payable is treated as debt for purposes
                                            of this calculation.

                                            (4)Based on treasury method for
                                            warrants outstanding and $10.00 share
                                            price.
                                            (5)Based on cash exercise of 13.7
                                            million warrants at $7.00 each and 14.4
                                            million warrants at $11.50 each.

    [GRAPHIC OMITTED]
    slide07

                                            Valuation Comparison
                                            Including Effects of Warrant
                                            Restructuring
    --------------------------------------  ---------------------------------------
    Iridium's fully-distributed valuation
    post-merger represents a 48% discount
    to the EBITDA multiple of its closest
    competitor, Inmarsat

    Iridium's valuation is made even more
    attractive by its higher growth and
    superior network coverage

    (All Values in Millions)
    Share Price                                  $10.00 (1)             $8.95(2)

    x Fully Diluted Shares Outstanding             71.8 (3)             459.5

                                          -------------             ----------
    Equity Value                                 $717.9              $4,111.0
    Net Debt/(Cash)                             ($93.0) (3)          $1,443.8
                                          -------------             ----------
    Enterprise Value                             $624.9              $5,554.8
    2009E EBITDA                          $120.0-$130.0 (4)            $580.3(5)

    ----------------------------------------------------------------------------
    Enterprise Value / 2009E EBITDA                5.0x (6)               9.6x
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    2008-2009E EBITDA Growth                         16%                   9%
    Network Coverage                             Global     No Polar Coverage

     (1) Estimated conversion amount per share.
     (2) Source: Bloomberg as of 7/28/09.
     (3) Estimated pro forma as of 3/31/09 assuming 30% of GHQ's existing public
         stockholders elect conversion for $10.00 in cash per share.
     (4) Source: Operational EBITDA guidance from GHQ press release dated 4/28/09.
     (5) Source: Bloomberg consensus estimates.
     (6) Based on midpoint of 2009E EBITDA guidance.

                                                                                   8

    [GRAPHIC OMITTED]
    slide08

                                            Anticipated Timetable to Closing
    --------------------------------------  ---------------------------------------

    []  Expecting Iridium to Announce Q2 Results During Week of August 10th

    []  Anticipating September GHQ Stockholder Vote on Acquisition of Iridium

    []  No Further Amendments to Economics or Other Terms Planned

    []  Completion Subject to FCC Approval and GHQ Stockholder Approval [GRAPHIC

    [GRAPHIC OMITTED]
    slide09