Frontier Communications has filed for Chapter 11 bankruptcy protection.

In a filing in the U.S. Bankruptcy Court for the Southern District of New York the company said it has reached an agreement with more than 75% of its bondholders on a restructuring plan that would reduce its debt by $10 billion.

If approved, the bankruptcy would be among the largest in the history of the telecoms industry.

Frontier said Goldman Sachs has arranged $460 million in debtor-in-possession financing and it has more than $700 million cash on hand. Its filing listed total debt of $21.9 billion and assets of $17.4 billion. It expects to sell $1.35 billion of territories in Washington, Oregon, Idaho, and Montana at the end of this month.

“With a recapitalized balance sheet, we will have the financial flexibility to reposition the company and accelerate its transformation by allocating capital resources and adding talent to enhance our service offerings to our customers while optimizing value for our stakeholders,” the chairman of the finance committee of the board of directors, Robert Schriesheim, said.

BlackRock is the company’s largest stockholder with 9% of shares. Vanguard Group and Charles Schwab each hold about 6%. The largest unsecured creditor identified by Frontier was the human resources software company PeopleScout.

Frontier bought the wireline operations of Verizon in California, Texas, and Florida for $10.5 billion in 2016.

“Serving the new territories proved more difficult and expensive than the [company] anticipated, and integration issues made it more difficult to retain customers,” FTI Consulting adviser Carlin Adrianopoli said in the filing. “Frontier has not been able to fully realize the economies of scale expected from the … [transactions], as evidenced by a loss of approximately 1.3 million customers.”

Frontier said it would continue service uninterrupted to its 4.1 million customers.