June 17, 2011

SIS update

Richmond, B. C. - MacDonald, Dettwiler and Associates Ltd. (TSX:MDA), a provider of essential information solutions, announced today that with Intelsat’s concurrence it is extending by about three months the requirements definition phase of its previously announced Satellite Infrastructure Servicing (SIS) initiative.

Since the press release dated March 15, 2011, the Company has been engaged in extensive discussions with potential government and commercial customers and regulators.

Extending the requirements definition phase will give the Company the opportunity to better understand the changes necessary to address the balance between potential commercial and government customers, to evaluate whether NASA intends to fund a competing solution to our commercial initiative, and to advance the dialogue with regulators, customers and suppliers.

About MDA

MDA provides advanced information solutions that capture and process vast amounts of data, produce essential information, and improve the decision making and operational performance of business and government organizations worldwide.

Focused on markets and customers with strong repeat business potential, MDA delivers a broad spectrum of information solutions, ranging from complex operational systems, to tailored information services, to electronic information products.

The Company's common shares trade on the Toronto Stock Exchange under the symbol (TSX: MDA).

Related Websites:
www.mdacorporation.com
www.intelsat.com