Document:

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                                                                     EXHIBIT 4.3

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        Segundo Convenio Modificatorio al Convenio Maestro Post-Escision
        ----------------------------------------------------------------

Segundo Convenio Modificatorio al Convenio Maestro Post-Escision celebrado, por
una parte, por Telefonos de Mexico, S.A. de C.V. (en lo sucesivo "Telmex"),
representada en este acto por su Director de Finanzas y Administracion, Adolfo
Cerezo Perez, y, por la otra parte, America Movil, S.A. de C.V., representada en
este acto por su Director de Finanzas y Administracion, Carlos Jose Garcia
Moreno Elizondo (en lo sucesivo "America Movil"), de acuerdo con las siguientes
declaraciones y clausulas:

                                  DECLARACIONES

Declaran las partes, por conducto de sus representantes, que:

1.  Con fecha 25 de septiembre de 2000 se llevo a cabo la Escision de Telmex
resuelta por la Asamblea General Extraordinaria de Accionistas de Telmex de esa
misma fecha (la "Asamblea").
                 --------

2.  En la Asamblea se resolvieron, entre otros puntos, que al surtir efectos la
escision y realizarse la aportacion en bloque que Telmex hizo a America Movil
como consecuencia de la escision, el importe del capital social de Telmex seria
de $402'900,048.30 M.N., el cual corresponderia integramente al capital minimo
fijo sin derecho a retiro; en tanto que, el capital minimo fijo con el que
quedaria constituida America Movil, tambien seria de $402'900,048.30 M.N. y
deberia quedar representado por 3,266'191,868 acciones de la Serie "AA" comunes
u ordinarias, nominativas, sin expresion de valor nominal; 345'648,701 acciones
de la Serie "A" comunes u ordinarias, nominativas, sin expresion de valor
nominal; y 12,504'161,363 acciones de la Serie "L", sin expresion de valor
nominal, de voto limitado; y al quedar constituida America Movil, se encontraria
en la tesoreria, para su recolocacion en los terminos del articulo 14 Bis 3 de
la Ley del Mercado de Valores, un total de 1,631'487,932 de dichas acciones de
la Serie "L". Asimismo, la Asamblea resolvio que las transmisiones de los
bloques patrimoniales se adecuarian, en su caso, a las cantidades,
caracteristicas y naturaleza juridica de los bienes y derechos existentes al
operarse la escision.

3.  Con fecha 18 de enero de 2001, celebraron un Convenio Maestro Post-Escision
(el "Convenio Post Escision"), por virtud del cual, entre otros acuerdos,
     ----------------------
establecieron ciertos servicios legales, financieros, contables, de relaciones
con inversionistas y otros de cualquiera otra indole que solicitara America
Movil o cualquiera de sus subsidiarias a Telmex o a cualquiera de sus
subsidiarias en los terminos de dicho Contrato.

4.  Con fecha 15 de marzo de 2001, celebraron un Primer Convenio Modificatorio
al Convenio Maestro Post-Escision.

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5.  Desean determinar algunas adecuaciones sobre los aspectos que mas adelante
se describen, derivado de lo que se senala en el acta de escision de Telmex y de
las operaciones con acciones de Telmex realizadas despues del 25 de septiembre
de 2000 y antes del Dia de la Entrega, y reconocer ciertos ajustes a sus libros
derivados de la Escision para concluir y finiquitar definitivamente los efectos
que dichas operaciones generaron entre America Movil y Telmex por la escision.

6.  En el Convenio Post Escision se definio como "Acciones Recompradas" tanto a
las acciones que se mantenian por Telmex antes de la Asamblea como aquellas
recompradas despues de la Asamblea y hasta el Dia de la Entrega, lo cual las
partes consideran debe modificarse dado el trato diferencial que debe tener cada
parte de acciones para los efectos de lo que previeron al convenir los acuerdos
contenidos en la Clausula Decimoquinta del Convenio Post Escision.

7.  Sus representantes tienen la autoridad y facultades suficientes para
celebrar el presente Convenio, las cuales no han sido limitadas ni modificadas
en forma alguna.

                                    CLAUSULAS

     Primera.  Las partes convienen en modificar, con efectos retroactivos al
25 de septiembre de 2000, la definicion de Acciones Recompradas a que se refiere
la Clausula Primera del Convenio Post Escision e insertar una nueva definicion
de Acciones Recompradas Post Escision, a fin de que en lo sucesivo queden
redactada de la siguiente manera:

    "Acciones Recompradas     Aquellas  acciones  que Telmex  mantenia en
                              tesoreria  al 25 de  septiembre  de 2000 , que
                              constituyen  las  1,631'487,932  acciones  a que
                              se  refiere  el  Anexo  "C" del acta de la
                              Asamblea indicada."

    "Acciones Recompradas
    Post Escision             Aquellas  acciones  recompradas  por Telmex del 26
                              de septiembre de 2000 hasta el Dia de la Entrega."

     Segunda.  Las partes convienen en modificar, con efectos a partir del 30
de abril de 2001, la Clausula Decimoquinta del Convenio Post Escision, a fin de
que en lo sucesivo quede redactada de la siguiente manera:

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     DECIMOQUINTA  ACCIONES RECOMPRADAS Y ACCIONES RECOMPRADAS POST ESCISION.
                   ---------------------------------------------------------

15.1  ACCIONES RECOMPRADAS:  Telmex cancelara el cupon correspondiente a la
      ---------------------
entrega de las Acciones de America Movil por la Escision de Telmex, respecto a
las Acciones Recompradas en los terminos de lo previsto por el ultimo parrafo de
la Disposicion Segunda de la Circular 11-16 y sus modificaciones expedida por la
entonces Comision Nacional de Valores el 27 de agosto de 1990 y demas
disposiciones legales aplicables.

15.2  ACCIONES RECOMPRADAS POST ESCISION:  Telmex cancelara el cupon
      ----------------------------------
correspondiente a la entrega de las Acciones de America Movil por la Escision de
Telmex, respecto a las Acciones Recompradas Post Escision en los terminos de lo
previsto por el ultimo parrafo de la Disposicion Segunda de la Circular 11-16 y
sus modificaciones expedida por la entonces Comision Nacional de Valores el 27
de agosto de 1990 y demas disposiciones legales aplicables. En consecuencia,
conforme a lo previsto en la Resolucion II.1 de la Asamblea General
Extraordinaria de Accionistas de Telmex del 25 de septiembre de 2000, las partes
ajustaran sus libros para reflejar los montos que se arrojaron en el Dia de
Entrega.

     Tercera.  Salvo por las modificaciones acordadas por virtud de las
Clausulas Primera y Segunda que anteceden, los demas terminos y condiciones del
Convenio Post Escision no se modifican y conservan por lo tanto, su misma fuerza
y alcances legales.

     Cuarta.  Este Convenio estara regido y sera ejecutado de conformidad con
las leyes aplicables en la Ciudad de Mexico, Distrito Federal. Asimismo, las
partes en caso de controversia, se someten a la jurisdiccion de los tribunales
competentes del Distrito Federal, renunciando a cualquier fuero que por razon de
su domicilio o por cualquier otra causa pudiese corresponderles.

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Este Convenio se firma por cada una de las partes en 2 (dos) tantos, cada uno de
los cuales se considerara un solo documento original el dia 30 de abril de 2001,
en la Ciudad de Mexico, Distrito Federal.

TELEFONOS DE MEXICO, S.A. DE C.V.

Por: /s/Adolfo Cerezo Perez
    ----------------------------------------
Nombre: Adolfo Cerezo Perez
Cargo: Director de Finanzas y Administracion

AMERICA MOVIL, S.A. DE C.V.

Por: /s/Carlos Jose Garcia Moreno E.
    ------------------------------------------
Nombre: Carlos Jose Garcia Moreno E.
Cargo: Director de Finanzas y Administracion

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                                                      UNOFFICIAL TRANSLATION FOR
                                                      --------------------------
                                                       INFORMATION PURPOSES ONLY
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          Second Amendment Agreement to Post-Spin-Off Master Agreement
          ------------------------------------------------------------

Second Amendment Agreement to the Post-Spin-Off Master Agreement entered into,
on one part, by Telefonos de Mexico, S.A. de C.V. (hereinafter referred to as
"Telmex") represented in this act by its Finance and Management Director, Adolfo
Cerezo Perez, and, on the other part, America Movil, S.A. de C.V. represented in
this act by its Finance and Management Director, Carlos Jose Garcia Moreno
Elizondo (hereinafter referred to as "America Movil"), pursuant to the following
                                      -------------
statements and clauses:

                                   STATEMENTS

The parties state, through their representatives, that:

1.  On September 25, 2000, the Telmex Spin-Off was carried by resolution of
Telmex Stockholders General Special Meeting of same date (the "Meeting").
                                                               -------

2.  Among other matters, the Meeting resolved that as the spin-off becomes
effective and the block contribution that Telmex made to America Movil was
carried out as a consequence of the spin-off, Telmex's capital stock would be
$402'900,048.30 pesos, which would fully correspond to the fixed minimum capital
and would not be entitled to withdrawals, while the minimum fixed capital with
which America Movil would be incorporated, would also be $402'900,048.30 pesos
and should be represented by 3,266'191,868 "AA" Series shares, either common or
ordinary, nominative, with no par value expressed; 345'648,701 "A" Series
shares, either common or ordinary, nominative, with no par value expressed; and
12,504'161,363 "L" Series shares, with no par value expressed, of limited vote,
and, upon incorporation of America Movil, a total of 1,631'487,932 of the
mentioned "L" Series shares would be in treasury for their replacement in terms
of article 14 Bis 3 of the Securities Market Law. In addition, the Meeting
determined that the transfers of the equity blocks would be adjusted, as
necessary, to the amounts, features and legal nature of assets and rights
existing at the time of the spin-off.

3.  On January 18, 2001, a Post-Spin-Off Master Agreement (the "Post-Spin-Off
                                                                -------------
Agreement") was entered into by virtue of which, among other agreements, certain
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legal, financing, accounting, relations with investors and other services of
whatever kind were established as requested by America Movil or any of its
subsidiaries to Telmex or any of its subsidiaries, subject to the terms of said
Agreement.

4.  On March 15, 2001, a First Amendment Agreement to the Post-Spin-Off Master
Agreement was entered into.

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5. The parties wish to modify certain matters, as further described deriving
from the content of Telmex spin-off minutes and the Telmex stock operations made
after September 25, 2000, and before the Delivery Date, and acknowledging
certain adjustments in its books derived from the Spin-Off to conclude and
definitely settle the effects such operations generated between America Movil
and Telmex by reason of the spin-off.

6. The Post-Spin-off Agreement defined both the shares held by Telmex before the
Meeting as well as the stock repurchased after the Meeting and up to the
Delivery Date, as "Repurchased Stock"; the parties consider that this should be
amended in view of the differential treatment each portion of shares should have
for the consequences of what they anticipated when they made the agreements
contained in the Fifteenth Clause of the Post-Spin-Off Agreement.

7. Their representatives have the sufficient authority and powers to enter into
the Agreement herein, which have not been limited nor modified in any way.

                                     CLAUSES

     First.  The parties agree to amend retroactively as of September 25, 2000,
the definition of Repurchased Stock referred to in the First Clause of the
Post-Spin-Off Agreement and include a new definition of the Post-Spin-off
Repurchased Stock, in order that henceforth they may be drafted and may read as
follows:

         "Repurchased Stock                 Shares held by Telmex in
                                            treasury on September 25, 2000,
                                            constituting 1,631'487,932 shares
                                            referred to in Exhibit "C" in
                                            minutes of the indicated Meeting".

         "Post-Spin-off Repurchased
          Stock                             Those shares repurchased by Telmex
                                            from September 26, 2000, until the
                                            Delivery Date".

     Second.  The parties agree to amend, with retroactive effects, as of April
30, 2001, the Fifteenth Clause of the Post-Spin-Off Agreement, in order that
henceforth it shall be drafted and may read as follows:

     FIFTEENTH  REPURCHASED STOCK AND POST-SPIN-OFF REPURCHASED STOCK
                -----------------------------------------------------

15.1  REPURCHASED STOCK:  Telmex shall cancel the corresponding coupon upon
      ------------------
delivery of America Movil shares by reason of the Telmex Spin-Off, regarding the
Repurchased Stock under the terms provided in last paragraph of Second Provision
in Circular 11-16 and its amendments issued by the - at that time - National
Securities Commission on August 27, 1990, and other legal applicable provisions.

15.2  POST-SPIN-OFF REPURCHASED STOCK:  Telmex shall cancel the corresponding
      --------------------------------
coupon upon delivery of the America Movil shares by reason of the Telmex
Spin-Off, regarding the Post-Spin-Off Repurchased Stock under the terms provided
in last paragraph of the Second Provision of Circular 11-16 and its

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amendments issued by the - at that time - National Securities Commission on
August 27, 1990, and other legal applicable provisions. Therefore, pursuant to
provisions in Resolution II.1 of Telmex Special General Stockholders Meeting on
September 25, 2000, the parties will adjust their financial statements to
reflect the amounts shown on the Delivery Date.

     Third.  Except for the amendments agreed upon by virtue of the preceding
First and Second Clauses, the other terms and conditions of the Post-Spin-Off
Agreement are not amended and therefore, retain the same force and significance
of law.

     Fourth.  This Agreement shall be governed and executed according to
applicable laws in the City of Mexico, Federal District. In addition, in case of
controversy, the parties are subject to the jurisdiction of the competent courts
of the Federal District, waiving any court that might correspond as per their
domicile or any other cause.

     This Agreement is executed by each party in 2 (two) copies, each copy shall
be considered one sole original document, on April 30, 2001, in the City of
Mexico, Federal District.

TELEFONOS DE MEXICO, S.A. DE C.V.

By: /s/Adolfo Cerezo Perez
   ---------------------------------------
Name: Adolfo Cerezo Perez
Position: Finance and Administration Director

AMERICA MOVIL, S.A. DE C.V.

By: /s/Carlos Jose Garcia Moreno E.
   -----------------------------------------
Name: Carlos Jose Garcia Moreno E.
Position: General Director and Attorney in Fact<PAGE>
                                                                    EXHIBIT 4.12

                                    AMENDMENT
                               TO THE AVIALL, INC.
                            1998 STOCK INCENTIVE PLAN

         THIS AMENDMENT TO THE AVIALL, INC. 1998 STOCK INCENTIVE PLAN (this
"Amendment"), dated as of June 14, 2002, is made and entered into by Aviall,
Inc., a Delaware corporation (the "Company"). Terms used in this Amendment with
initial capital letters that are not otherwise defined herein shall have the
meanings ascribed to such terms in the Aviall, Inc. 1998 Stock Incentive Plan
(the "Plan").

                                    RECITALS

         WHEREAS, Section 16 of the Plan provides that the Board of Directors of
the Company (the "Board") may amend the Plan at any time;

         WHEREAS, the Board desires to amend the Plan to increase the aggregate
number of Common Shares (as defined in the Plan) that may be issued or
transferred under the Plan set forth in Section 3 of the Plan; and

         WHEREAS, the Board submitted the proposal to amend the Plan to the
Company's stockholders at the 2002 Annual Meeting of Stockholders; and

         WHEREAS, the Company's stockholders approved the proposal to amend the
Plan to increase the aggregate number of Common Shares;

         NOW, THEREFORE, in accordance with Section 16 of the Plan, the Company
hereby amends the Plan as follows:

1. Subsection 3(a) of the Plan is hereby amended, effective June 14, 2002, by
deleting said Subsection in its entirety and substituting in lieu thereof the
following:

         (a) Subject to adjustment as provided in Section 3(b) and Section 10 of
         this Plan, the number of Common Shares that may be issued or
         transferred (i) upon the exercise of Option Rights or Appreciation
         Rights, (ii) as Restricted Shares and released from substantial risks
         of forfeiture thereof, (iii) as Deferred Shares, (iv) in payment of
         Performance Shares or Performance Units that have been earned, or (v)
         in payment of dividend equivalents paid with respect to awards made
         under the Plan shall not exceed in the aggregate 3,290,000 Common
         Shares, plus any shares described in Section 3(b). Such shares may be
         shares of original issuance or treasury shares or a combination of the
         foregoing.

2. Subsection (3)(c)(i) of the Plan is hereby amended, effective June 14, 2002,
by deleting said Subsection in its entirety and substituting in lieu thereof the
following:

         (i) the aggregate number of Common Shares actually issued or
         transferred by the Company upon the exercise of Incentive Stock Options
         shall not exceed 3,290,000 Common Shares, and

3. Except as expressly amended by this Amendment, the Plan shall continue in
full force and effect in accordance with the provisions thereof.

<PAGE>

         IN WITNESS WHEREOF, the Company has caused this Amendment to be duly
executed as of the date first written above.

                                      AVIALL, INC.

                                      By:    /s/ Jeffrey J. Murphy
                                             -----------------------------------
                                      Name:  Jeffrey J. Murphy
                                      Title: Senior Vice President, Law & Human
                                             Resources, Secretary and General
                                             Counsel

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