Bronco Drilling SC 13D/A Bronco Drilling / HELU CARLOS SLIM ownership change

EXHIBIT 99.1

JOINT FILING AGREEMENT

THIS JOINT FILING AGREEMENT (this “Agreement”) is made and entered into as of this 3rd day of March 2010, by and among Carlos Slim Helú, Carlos Slim Domit, Marco Antonio Slim Domit, Patrick Slim Domit, María Soumaya Slim Domit, Vanessa Paola Slim Domit, Johanna Monique Slim Domit, Inmobiliaria Carso, S.A. de C.V., Banco Inbursa, S.A. Institucion de Banca Multiple Grupo Financiero Inbursa, and Carso Infraestructura y Construcción, S.A.B. de C.V.

The parties to this Agreement hereby agree to prepare jointly and file timely (and otherwise to deliver as appropriate) all filings on any Form 3, 4 or 5 or Schedule 13D or 13G relating to their ownership (direct or otherwise) of any securities of Bronco Drilling Company, Inc., a Delaware corporation, and any and all amendments thereto and any other document relating thereto (collectively, the “Filings”) required to be filed by them pursuant to the Securities Exchange Act of 1934, as amended. Each party to this Agreement further agrees and covenants to the other parties that it will fully cooperate with such other parties in the preparation and timely filing (and other delivery) of all such Filings.

IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the date first set forth above.

CARLOS SLIM HELÚ
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
CARLOS SLIM DOMIT
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
MARCO ANTONIO SLIM DOMIT
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
PATRICK SLIM DOMIT
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**

1

MARIA SOUMAYA SLIM DOMIT
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
VANESSA PAOLA SLIM DOMIT
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
JOHANNA MONIQUE SLIM DOMIT
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
INMOBILIARIA CARSO, S.A. DE C.V.
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact**
BANCO INBURSA, S.A. INSTITUCION DE BANCA MULTIPLE GRUPO FINANCIERO INBURSA
By:	/s/ Raul Humberto Zepeda Ruiz
	Name: Raul Humberto Zepeda Ruiz
	Title: Attorney-In-Fact***
CARSO INFRAESTRUCTURA Y CONSTRUCCIÓN, S.A.B. de C.V.
By:	/s/ Eduardo Valdes Acra
	Name: Eduardo Valdes Acra
	Title: Attorney-In-Fact****

_______________________

** The Powers of Attorney given by the members of the Slim Family and Inmobiliaria were previously filed with the Securities and Exchange Commission on October 22, 2008, as exhibits to a statement on Schedule 13G filed by the Reporting Persons with respect to Bronco Drilling Company, Inc.

*** The Power of Attorney given by Banco Inbursa was previously filed with the Securities and Exchange Commission on February 14, 2005, as an exhibit to a statement on Schedule 13G filed by the Slim Family, Banco Inbursa and certain other persons with respect to MCI, Inc.

**** The Power of Attorney given by Carso Infraestructura y Construcción was previously filed with the Securities and Exchange Commission on February 5, 2007, as an exhibit to a statement on Schedule 13G filed by the Reporting Persons with respect to Allis Chalmers Energy Inc.

2