THIRD AMENDMENT TO TERM LOAN AGREEMENT

Exhibit 10.55

THIRD AMENDMENT TO TERM LOAN AGREEMENT

This Third Amendment to Term Loan Agreement (this “Amendment”) is made as of February 20, 2015, by and among AMERICAN TOWER CORPORATION, as Borrower (the “Borrower”), THE ROYAL BANK OF SCOTLAND PLC, as Administrative Agent (the “Administrative Agent”), and the financial institutions whose names appear as lenders on the signature page hereof.

WHEREAS, the Borrower and the Administrative Agent are party to that certain Term Loan Agreement, dated as of October 29, 2013 (as amended, restated, extended, supplemented or otherwise modified in writing from time to time, the “Loan Agreement”) among the Borrower, the Administrative Agent and the Lenders from time to time party thereto.

WHEREAS, the Borrower, the Administrative Agent and the Lenders who are signatories hereto and who constitute Majority Lenders have agreed to amend the Loan Agreement pursuant to Section 11.11 of the Loan Agreement.

WHEREAS, pursuant to Section 2.13 of the Loan Agreement, the Borrower has requested Incremental Term Loan Commitments in an aggregate amount of $500,000,000.

NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged by each of the parties hereto, the parties hereby agree as follows:

1. DEFINED TERMS. Unless otherwise defined herein, capitalized terms used herein shall have the meanings given to them in the Loan Agreement.

2. AMENDMENT. The Loan Agreement is hereby amended as follows:

(a) Section 1.1 of the Loan Agreement is hereby amended by inserting the following definition of “Verizon Transaction”:

“Verizon Transaction” means that certain transaction among the Borrower, Verizon Communications, Inc. and certain of their affiliates pursuant to that certain Master Agreement dated February 5, 2015.”

(b) Section 2.13 of the Loan Agreement is hereby amended by deleting “$500,000,000” in clause (iii) thereof and replacing it with “$1,000,000,000”.

(c) Section 7.6 of the Loan Agreement is hereby amended by deleting the text thereof and inserting in its place the following:

“As of the end of each fiscal quarter, the Borrower shall not permit the ratio of (a) Total Debt on such calculation date to (b) Adjusted EBITDA, as of the last day of such fiscal quarter to be greater than (i) for the fiscal quarters ended December 31, 2014 through the end of the fiscal quarter ended immediately prior to the closing of

the Verizon Transaction, 6.00 to 1.00, (ii) for the first and second fiscal quarters ending on or after the closing of the Verizon Transaction, 7.25 to 1.00, (iii) for the two subsequent fiscal quarters, 7.00 to 1.00 and (iv) thereafter, 6.00 to 1.00, provided, that, solely for purposes of Section 7.1(i)(ii) and the determination of pro forma compliance, the ratio shall be deemed to be 7.25 to 1.00 as of the end of the fiscal quarter ended immediately prior to the closing of the Verizon Transaction.”

3. BRING-DOWN OF REPRESENTATIONS. The Borrower hereby certifies that, as of the date of this Amendment, (i) the representations and warranties contained in Section 4.1 of the Loan Agreement are true and correct in all material respects, except for those representations and warranties that are qualified by materiality or Materially Adverse Effect, which shall be true and correct, both before and after giving effect to this Amendment, and after giving effect to any updates to information provided to the Lenders in accordance with the terms of the Loan Agreement except to the extent stated to have been made as of the Agreement Date, and (ii) no Default exists.

4. EFFECTIVENESS. This Amendment shall become effective upon the Administrative Agent receiving this Amendment duly executed by the Borrower and the Majority Lenders.

5. NO OTHER AMENDMENTS. Except as provided herein, each of the other provisions of the Loan Agreement shall remain in full force and effect.

6. COUNTERPARTS. This Amendment may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such separate counterparts shall together constitute one and the same instrument. Delivery of an executed counterpart of a signature page to this Amendment by telecopier or electronic transmission shall be effective as delivery of a manually executed counterpart.

7. GOVERNING LAW. This Amendment shall be construed in accordance with and governed by the internal laws of the State of New York applicable to agreements made and performed in the State of New York.

8. MISCELLANEOUS.

(a) On and after the effective date of this Amendment, each reference in the Loan Agreement to “this Agreement,” “hereunder,” “hereof” or words of like import referring to the Loan Agreement shall mean and be a reference to the Loan Agreement, as amended by this Amendment.

(b) The execution, delivery and effectiveness of this Amendment shall not, except as expressly provided herein, operate as a waiver of any right, power or remedy of any Lender or the Administrative Agent under any of the Loan Documents, nor constitute a waiver of any provision of any of the Loan Documents.

(c) On and after the effectiveness of this Amendment, this Amendment shall for all purposes constitute a Loan Document.

IN WITNESS WHEREOF, the parties hereto have executed this Amendment or caused it to be executed by their duly authorized officers, all as of the day and year above written.

[Signature Page to Third Amendment to Term Loan Agreement]

[Signature Page to Third Amendment to Term Loan Agreement]

[Signature Page to Third Amendment to Term Loan Agreement]

[Signature Page to Third Amendment to Term Loan Agreement]

[Signature Page to Third Amendment to Term Loan Agreement]

[Signature Page to Third Amendment to Term Loan Agreement]