What American Tower Corporation told the SEC could break it.

American Tower derives a large portion of revenue from a small number of customers — T-Mobile (18%), AT&T (17%), Verizon Wireless (14%) and Telefónica (10%) together ~59% in 2025 — so carrier financial difficulties, bankruptcy, consolidation or non-renewal could materially reduce revenue.

“The following is a list of significant customers (representing at least 10% of revenue in any of the last three years)... T-Mobile 18 % 19 % 19 % AT&T 17 % 18 % 18 % Verizon Wireless 14 % 13 % 14 % Telefónica 10 % 10 % 10 %”

American Tower is in an arbitration with AT&T Mexico (AT&T Comunicaciones Digitales and related entities), which represented ~$300 million of tenant revenue in 2025 and is challenging the monthly lease-amount calculation under their Master agreement — an adverse outcome could reduce revenue.

“we are currently engaged in a legal dispute (the “Arbitration”) with one of our customers in Mexico, AT&T Comunicaciones Digitales, S. de R.L. de C.V. and related entities (collectively, “AT&T Mexico”). AT&T Mexico, which represented approximately $300 million of tenant revenue in 2025, is challenging the calculation of the monthly lease amount”

American Tower's data-center business relies on third parties, governmental entities and suppliers for sufficient power (and on third-party internet/telecom/utility providers); it also depends on landlords to maintain leased data centers — difficulties securing contracted energy/capacity or inadequate landlord maintenance could disrupt operations or force early exits.

“we rely on third parties, governmental entities and suppliers to provide sufficient power for our data centers and to support future expansion... Additionally, we rely on third-party providers for internet, telecommunications and utilities, and any failure by these providers could adversely affect our business”

New-tower construction and modifications may require FCC and FAA pre-approval (registration, height/airfield-proximity, FAA-standard maintenance) plus environmental review in the U.S. and similar regimes abroad; non-compliance can bring monetary penalties or site-deconstruction orders, and AMT must also meet REIT 90%-distribution requirements.

“the construction of new towers or modifications to existing towers may require pre-approval by the Federal Communications Commission (“FCC”) and the Federal Aviation Administration (“FAA”)... Non-compliance with applicable tower-related requirements may lead to monetary penalties or site deconstruction orders.”