Document:

EXHIBIT 10.8.4

                ACKNOWLEDGMENT, CONSENT AND AGREEMENT (MSN 22237)

            ATLAS  AIR  WORLDWIDE   HOLDINGS,   INC.,  a  Delaware   corporation
("GUARANTOR"), with reference to the Guaranty, dated as of November 9, 2001 (the
"GUARANTY"),  made by  Guarantor  in favor of Polaris  Holding  Company  and its
successors  and assigns  ("GUARANTEED  PARTY")  relating to the  Aircraft  Lease
Agreement,  dated as of October 24, 2001,  between Polaris Holding  Company,  as
lessor,  and  Polar  Air  Cargo,  Inc.,  as  lessee,  as  supplemented  by Lease
Supplement  No. 1 dated  November  9, 2001 and the  Letter  Agreement  No. 1 (as
defined in such Aircraft Lease  Agreement),  and as assigned by Polaris  Holding
Company to Polaris  Aircraft  (Pacific Rim),  Inc.,  assumed by Polaris Aircraft
(Pacific Rim),  Inc. and amended  pursuant to the Aircraft Lease  Assignment and
Amendment  Agreement,  dated as of June 23, 2003, among Polaris Holding Company,
Polaris  Aircraft  (Pacific  Rim),  Inc.  ("LESSOR")  and Polar Air Cargo,  Inc.
("LESSEE")  (as so  supplemented  and as so assigned and  amended,  the "LEASE";
capitalized  terms used herein but not defined herein having the meanings stated
or ascribed in the Lease), and to the other Operative Documents, DOES HEREBY (in
each case, for the benefit of the Guaranteed  Party and, in each case (except to
the  extent  otherwise  provided  herein),  without  limitation  of any  term or
provision of the Guaranty):

                  (i)  ACKNOWLEDGE  receipt  (pursuant to and as required by the
      Guaranty)  of  notice  of (a)  the  amendment  of the  Lease  pursuant  to
      Amendment  Agreement  (MSN  22237),  dated as of August 1,  2003,  between
      Lessor and  Lessee  (the  "LEASE  AMENDMENT"),  and (b) the  Restructuring
      Letter Agreement (MSN 22237),  dated as of August 1, 2003,  between Lessor
      and Lessee which is referred to in the Lease Amendment (THE "RESTRUCTURING
      LETTER AGREEMENT");

                  (ii)  CONSENT  to (a) the  terms and  provisions  of the Lease
      Amendment  and the  Restructuring  Letter  Agreement,  (b) the  execution,
      delivery  and  performance  thereof  by  Lessor  and  Lessee,  and (c) the
      amendment of the Lease pursuant thereto and on the terms provided therein;

                  (iii)  AGREE  that,  from and  after  the  Effective  Date (as
      defined in the Lease  Amendment),  (a) any reference in the Guaranty,  the
      Lease or any other Operative Document,  or otherwise by Guarantor,  to the
      Lease shall mean the Lease, as amended by the Lease Amendment  (including,
      without  limitation,  the references  therein to the Restructuring  Letter
      Agreement),  and (b) any reference by Guarantor or Guaranteed Party to the
      Guaranty shall mean the Guaranty, as supplemented hereby; and

                  (iv) AGREE that, except as supplemented  hereby,  the Guaranty
      shall  remain in full force and effect as in  existence on the date hereof
      and is hereby ratified and confirmed in all respects.

                            [Signature Page Follows]

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            IN  WITNESS  WHEREOF,  Guarantor  has  caused  this  Acknowledgment,
Consent  and  Agreement  to be  executed  and  delivered  as of this 18th day of
November, 2003.

                                         ATLAS AIR WORLDWIDE HOLDINGS, INC.

                                         By /s/ Jeffrey H. Erickson
                                            ------------------------------------
                                            Name: Jeffrey H. Erickson
                                            Title: President & COO

      [Signature Page to Acknowledgment, Consent and Agreement (MSN 22237)]EXHIBIT 10.8.5

                                 GUARANTY 22237

            GUARANTY 22237, dated as of July 27, 2004 (this "GUARANTY"), of
ATLAS AIR, INC., a Delaware corporation (together with its successors and
assigns, "ATLAS") in favor of POLARIS AIRCRAFT (PACIFIC RIM), INC., a California
corporation, as lessor under the Lease (as defined below) (together with its
successors and assigns, the "GUARANTEED PARTY").

            WHEREAS, the Guaranteed Party is a party to that certain Aircraft
Lease Agreement (MSN 30808), dated as of October 24, 2001 (as supplemented by
Lease Supplement No. 1 dated November 9, 2001, the "LEASE"), between the
Guaranteed Party, as lessor, and Polar Air Cargo, Inc., as lessee ("POLAR");

            WHEREAS, the Guaranteed Party is a party to that certain Amendment
Agreement (MSN 22237) to the Lease, dated as of August 1, 2003 (the "LEASE
AMENDMENT"), between Guaranteed Party and Polar;

            WHEREAS, Atlas is an Affiliate of Polar and it is of direct benefit
to Atlas and is in the furtherance of Atlas' business interests that Guaranteed
Party enter into the Lease Amendment; and

            WHEREAS, as an inducement for the Guaranteed Party's willingness to
enter into the Lease Amendment, Atlas has agreed to guarantee the obligations of
Polar arising under (i) the Lease, as amended by the Lease Amendment, and (ii)
each Other Agreement (as defined in the Lease, as amended by the Lease
Amendment). Capitalized terms not otherwise defined herein shall have the
meaning set forth in the Lease, as amended by the Lease Amendment;

            NOW, THEREFORE, in consideration of the premises and covenants
hereinafter contained and for other good and valuable consideration, the
sufficiency and receipt of which are hereby acknowledged. Atlas hereby agrees
for the benefit of the Guaranteed Party and the Guaranteed Party hereby
acknowledges:

            SECTION 1. GUARANTY BY ATLAS. (a) Atlas hereby irrevocably and
unconditionally guarantees, as primary obligor and not as a surety, (i) the due
and punctual performance by Polar of all of its obligations under (l) the Lease,
as amended by the Lease Amendment, and (3) each Other Agreement (collectively,
as amended, supplemented or otherwise modified from time to time, the "OPERATIVE
DOCUMENTS"), (ii) the due, punctual, prompt and complete payment when due of any
and all amounts which are from time to time due and payable by Polar pursuant to
the provisions of the Operative Documents after any applicable grace periods or
notice requirements if any, according to the terms thereof and (iii) all sums
for which Polar is or at any time becomes liable by reason of any breach of or
failure to per-

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form or observe, or any other noncompliance with, any covenant, condition,
agreement or other obligation to be performed by Polar under any Operative
Document, or the falsity of any representation or warranty of Polar in any
Operative Document (each of the foregoing (i), (ii) and (iii), including all
interest accruing thereon after the commencement of any bankruptcy, insolvency,
reorganization or similar proceeding, regardless of whether or not a claim can
be made or realized therefor, collectively, the "OBLIGATIONS"). Atlas agrees
that this Guaranty is a guarantee of performance and payment and not of
collection. Atlas hereby agrees that its obligations hereunder shall be primary,
absolute and unconditional, irrespective of, and unaffected by: (i) any
difference between the law selected as the governing law of the Operative
Documents and the law selected as the governing law of this Guaranty; (ii) the
existence, value or condition of or failure by the Guaranteed Party to perfect
any lien against the Aircraft or the release of any lien against the Aircraft,
including the Airframe, any Engine or any Part thereof, with respect to the
payment and performance by Polar of its performance and payment obligations
under the Operative Documents or any action, or the absence of any action, by
the Guaranteed Party in respect thereof (including, without limitation, the
release of any such security); (iii) the insolvency of Polar, Atlas or any
Affiliate thereof; (iv) the validity, regularity, legality or enforceability of
any Operative Document, any of the Obligations or any collateral security or
other guaranty therefor at any time or from time to time held by the Guaranteed
Party; (v) any defense, offset or counterclaim which may at any time be
available to or be asserted by Polar or Atlas against the Guaranteed Party; (vi)
any rejection of the Lease, as amended by the Lease Amendment or any related
document by Polar in any bankruptcy, reorganization or similar proceedings
related thereof; (vii) any extension, modification (including any increase),
indulgence or renewal with respect to any Obligations; (viii) any limitation of
the liability of Polar under any Operative Document that may now or hereafter be
imposed by any stature, regulation or rule of law, unless such limitation
applies to Atlas by mandatory provisions or law; (ix) any waiver, compromise,
consent, delay or other action or inaction or any exercise or non-exercise of
any right, remedy or power with respect to Polar or any Affiliate thereof; (x)
any change in the structure, ownership or control of Polar, Atlas or any
Affiliate thereof; (xi) any bankruptcy, reorganization, arrangement, adjustment,
composition, liquidation, dissolution or similar proceeding with respect to
Polar, Atlas or any Affiliate thereof; (xii) the appointment or a custodian,
receiver, trustee or other officer with similar powers with respect to Polar or
Atlas or any substantial part of their respective properties or (xiii) any other
event or circumstance whatsoever which may constitute, or might be construed to
constitute, an equitable or legal discharge of a surety or Atlas, it being the
purpose and intent of Atlas that this Guaranty and Atlas' obligations hereunder
shall remain in full force and effect and be binding upon Atlas and its
successors until the Obligations and the obligations of Atlas under this
Guaranty shall have been satisfied by indefeasible payment in full. Atlas waives
expressly and irrevocably, on behalf of itself and any successors or permitted
assigns (including any surety) any and all notice of the [ILLEGIBLE] renewal,
extension or accrual of any of the Obligations and [ILLEGIBLE] of or proof of
reliance by the Guaranteed Party upon this Guaranty or acceptance or this
Guaranty. Any [ILLEGIBLE] of the Obligations shall conclusively be deemed to
have been [ILLEGIBLE], [ILLEGIBLE] or [ILLEGIBLE] , or renewed, extended,

<PAGE>

amended or waived in reliance upon this Guaranty and all dealings between Polar
or Atlas and the Guaranteed Party shall likewise be conclusively presumed to
have been had or consummated in reliance upon this Guaranty. Except for the
notice provisions specifically set forth in the applicable Operative Documents
with respect to Polar, Atlas hereby waives diligence, presentment, protest,
demand for payment and notice of default or nonpayment to or upon Polar or Atlas
with respect to the performance and the payment obligations arising hereunder or
pursuant to the Operative Documents. Atlas further agrees that its guaranty of
the Obligations shall remain in full force and effect notwithstanding, and it
shall not be required to consent to any amendment or modification (including an
increase in the Obligations) of, or waiver, consent or extension with respect to
the Operative Documents that may be made or given as provided therein. Atlas
[ILLEGIBLE] that this Guaranty will not be discharged except by complete payment
and performance of the Obligations.

            (b) Atlas shall be subrogated to all rights of the Guaranteed Party
in respect of any amounts paid by Atlas pursuant to the provisions of this
Guaranty; PROVIDED, HOWEVER, that Atlas shall be entitled to enforce or to
receive any payments arising out of or based upon, such right of subrogation
only after all performance and amounts owed to the Guaranteed Party under the
Operative Documents have been satisfied and paid in full.

            (c) This Guaranty shall continue to be effective or be reinstated,
as the case may be, if at any time any payment or performance of the Obligations
owed to the Guaranteed Party is rescinded or must otherwise be returned by the
Guaranteed Party upon the insolvency, bankruptcy or reorganization of Atlas or
Polar or otherwise all as though such payment or performance had not been made.

            SECTION 2. REPRESENTATION AND WARRANTIES. Atlas hereby represents
and warrants, for the benefit of the Guaranteed Party, that:

                  (a) Atlas is a corporation duly organized, validly existing
            and in good standing under the laws of its jurisdiction of
            incorporation, is duly qualified as a foreign corporation and
            authorized to do business in each jurisdiction where the failure to
            be so qualified or in good standing would have a materially adverse
            effect on its business or financial condition, is an Affiliate of
            Polar and has the corporate power to own its properties and carry on
            its business as now conducted;

                  (b) Atlas has full power, authority, and legal right to
            execute, deliver and perform this Guaranty, and Atlas has taken all
            necessary corporate action to authorize such execution, delivery and
            performance;

                  (c) this Guaranty has been duly authorized, executed and
            delivered by Atlas and constitutes the legal, valid and binding
            obligation of Atlas, enforceable in accordance with its terms,
            except as such enforceability may be

<PAGE>

            limited by bankruptcy, insolvency, reorganization, receivership,
            moratorium, fraudulent transfer and conveyance, and other similar
            laws affecting the rights and remedies of creditors or the
            Guaranteed Party generally, and by general principles of equity,
            whether considered in a proceeding at law or in equity;

                  (d) no consent of any Person (including stockholders or any
            trustee or holder of any obligations of Atlas), and no consent,
            license, approval or authorization of, or registration or filing
            with, any governmental authority, bureau or agency is required in
            connection with the execution, delivery and performance of, and
            payment under this Guaranty, except such consents as have been duly
            obtained; and

                  (e) the execution, delivery, performance and payment of this
            Guaranty by Atlas do not and will not contravene any applicable law,
            regulation, order or decree, the organizational or governing
            documents of Atlas and do not and will not constitute a default
            under any provision of any indenture, mortgage, contract or other
            agreement to which Atlas is a party or by which any of its assets
            may be bound, which default could have a material adverse effect on
            Atlas' business or financial condition.

            SECTION 3. NOTICES. All notices to Atlas under this Guaranty, until
Atlas furnishes written notice to the contrary, shall be in writing and mailed,
faxed or delivered to Atlas Air Worldwide Holdings, Inc., 2000 Westchester
Avenue, Purchase, New York 10577-2543, and directed to the attention of the
General Counsel of Atlas Air Worldwide Holdings, Inc. (facsimile no. (914)
701-8333).

            SECTION 4. MISCELLEANEOUS. This Guaranty shall: (i) be binding upon
Atlas, its successors and permitted assigns including any debt [ILLEGIBLE]
possession on behalf of Atlas); (ii) inure to the benefit of and be enforceable
by the Guaranteed Party and its respective successors and assigns and its
Affiliates (and shall be transferable without Atlas' consent by the Guaranteed
Party in connection with the transfer of the Obligations under and in accordance
with the terms of the Operative Documents), but shall not and is not intended
to, create rights in any other third parties; (iii) not be waived, amended or
modified without the written consent of the Guaranteed Party; (iv) BE GOVERNED
BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK (INCLUDING
SECTIONS 5-1401 AND 5-1402 OF THE NEW YORK GENERAL OBLIGATIONS LAW) and (v) may
not be assigned, delegated, pledged, encumbered, hypothecated or transferred in
whole or in part by Atlas hereunder [ILLEGIBLE] to the fullest extent permitted
by applicable law, any and all rights [ILLEGIBLE] by jury in any legal
proceeding arising out of or relating to this Guaranty or the transactions
[ILLEGIBLE] hereby.

            (b) No failure or delay on the part of the Guaranteed Party in
exercising any right, power or privilege hereunder shall operate as a waiver
thereof, nor shall any delay

<PAGE>

or single or partial exercise of any right, power or privilege hereunder
preclude any other or further exercise thereof or the exercise of any other
right, power or privilege. The rights and remedies provided in and contemplated
by this Guaranty are cumulative and not exclusive of any rights or remedies
provided by law or as equity.

            (c) Atlas irrevocably agrees for the benefit of the Guaranteed
Party, by execution and delivery of this Guaranty that any legal action or
proceeding brought against Atlas with respect to this Guaranty or the
transactions contemplated hereby or by the Operative Documents may be brought
and determined in the courts of the State of New York, New York County, or in
the United States District Court for the Southern District of New York located
in the Borough of Manhattan and Atlas hereby irrevocable accepts with regard to
any such action or proceeding, for itself and in respect of its properties,
generally and unconditionally, the non-exclusive jurisdiction of the aforesaid
courts. Nothing herein shall affect the right of the Guaranteed Party to serve
process in any manner permitted by law as to commence legal proceedings or
otherwise to proceed against Atlas in any other jurisdiction in which Atlas may
be subject to suit.

            (d) Any provision of this Guaranty which is determined by competent
authority to be prohibited and unenforceable in any jurisdiction shall as to
such jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof, and any
such prohibition or enforceability in any jurisdiction shall not invalidate or
render unenforceable such provisions in any other jurisdiction.

            SECTION 5. INTERPRETATION. The headings of the sections and other
subdivisions of this Guaranty are inserted for convenience only and shall not be
deemed to constitute a part hereof.

            SECTION 6. ATTORNEY'S COST. Atlas agrees to pay all reasonable
attorney's fees and disbursements and all other actual costs and expenses that
may be incurred by the Guaranteed Party in the enforcement of this Guaranty,
whether or not an action at law is commenced with respect hereto.

            SECTION 7. WAIVER. In addition to the waivers contained in Section 4
hereof, Atlas waives, and agrees that it shall not at any time insist upon,
plead or claim any appraisal, valuation, stay, extension, marshaling of assets
or redemption laws, or exemption (which would not have been available to Polar),
whether now or at any time hereafter in force, which will delay, prevent or
otherwise affect the performance by Atlas of its performance and payment
obligations under or materially and adversely affect the enforcement by the
Guaranteed Party of this Guaranty. Atlas hereby waives the benefit of all
provisions of law which conflict with the terms of this Guaranty are not subject
to any offsets or defenses against the Guaranteed Party.

<PAGE>

            SECTION 8. REINSTATEMENT. This Guaranty shall remain in full force
and effect and continue to be effective should any petition be filed by or
against Polar or Atlas for liquidation or reorganization should Polar or Atlas
become insolvent or make an assignment for the benefit of creditors or should a
receiver or trustee be appointed for all or any significant part of such Polar's
or Atlas' assets, and shall continue to be effective or be reinstated, as the
case may be, if at any time payment and performance of the Obligations, or any
part thereof, pursuant to applicable law, is rescinded or reduced in amount, or
must otherwise be restored or returned by the Guaranteed Party, whether as a
"voidable preference" , "fraudulent conveyance", or otherwise, all as though
such payment or performance had not been made. In the event that any payment or
performance or any part thereof, is rescinded, reduced, restored or returned,
the related payment or obligation shall be reinstated and deemed reduced only by
such amount paid or performance received and not so rescinded, reduced, restored
or returned.

            SECTION 9. CURRENCY OF PAYMENT. Any payment to be made by Atlas
shall be made on an after-tax basis in the same currency as designated for
payment in the Lease and such designation of the currency of payment is of the
essence.

                            [SIGNATURE PAGE FOLLOWS]

<PAGE>

            IN WITNESS WHEREOF, the undersigned has caused this Guaranty to be
executed by its duly authorized officer as of the day, month and year first
above written.

                                           ATLAS AIR, INC.

                                           By: /s/ William C. Bradley
                                               ---------------------------------
                                               Name:  William C. Bradley
                                               Title: Vice President & Treasurer

                           ACKNOWLEDGMENT AND ACCEPTANCE

Polaris Aircraft (Pacific Rim), Inc. hereby acknowledges and accepts the
provisions of the foregoing Guaranty.

                                           POLARIS AIRCRAFT (PACIFIC RIM), INC.

                                           By:
                                               ---------------------------------
                                               Name:
                                               Title:

                       [SIGNATURE PAGE FOR GUARANTY 22237]

<PAGE>

            IN WITNESS WHEREOF, the undersigned has caused this Guaranty to be
executed by its duly authorized officer as of the day, month and year first
above written.

                                           ATLAS AIR, INC.

                                           By:
                                               ---------------------------------
                                               Name:
                                               Title:

                           ACKNOWLEDGMENT AND ACCEPTANCE

Polaris Aircraft (Pacific Rim), Inc. hereby acknowledges and accepts the
provisions of the foregoing Guaranty.

                                           POLARIS AIRCRAFT (PACIFIC RIM), INC.

                                           By: /s/ Keith A. Helming
                                               ---------------------------------
                                               Name:  Keith A. Helming
                                               Title: Vice President

                       [SIGNATURE PAGE FOR GUARANTY 22237]

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