Exhibit 23.1

CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

      As independent public accountants, we hereby consent to the incorporation by reference in this registration statement on Form S-3, filed by XO Communications, Inc. (formerly Nextlink Communications, Inc.) (the “Company”), of our report dated February 14, 2000 included in the Company’s Form 10-K for the year ended December 31, 1999 and to all references to our Firm included in this registration statement.

/s/ Arthur Andersen LLP

Vienna, Virginia
January 18, 2001