Exhibit 5.1

Brent B. Siler

T: +1 202 728 7040

bsiler@cooley.com

May 15, 2015

Iridium Communications Inc.

1750 Tysons Boulevard, Suite 1400

McLean, Virginia 22012

Ladies and Gentlemen:

You have requested our opinion with respect to certain matters in connection with the filing by Iridium Communications Inc., a Delaware corporation (the “Company”), of a Registration Statement on Form S-8 (the “Registration Statement”) with the Securities and Exchange Commission covering the offering of up to 23,203,009 shares of the Company’s common stock, par value $0.001 per share (the “Shares”), pursuant to the Company’s 2015 Equity Incentive Plan (the “2015 Plan”).

In connection with this opinion, we have examined and relied upon the Registration Statement and the related prospectus, the 2015 Plan, the Company’s Amended and Restated Certificate of Incorporation, as amended, and the Company’s Amended and Restated Bylaws, each as currently in effect, and the originals or copies certified to our satisfaction of such records, documents, certificates, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. We have assumed the genuineness and authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies and the due execution and delivery of all documents where due execution and delivery are a prerequisite to the effectiveness thereof.

Our opinion is expressed only with respect to the General Corporation Law of the State of Delaware. We express no opinion as to whether the laws of any particular jurisdiction other than those identified above are applicable to the subject matter of this opinion.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold and issued in accordance with the 2015 Plan, the Registration Statement and related prospectus, will be validly issued, fully paid and nonassessable.

We consent to the filing of this opinion as an exhibit to the Registration Statement.

Sincerely,

COOLEY LLP

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