Press Release

June 27, 2000

OpenAir and Concentric Form Strategic Partnership to Offer Users Additional Internet Business Service Solutions

Small and Medium-Sized Companies Will Have Access to OpenAir Business Services Through Concentric's Gateway

Boston (June 27, 2000) – A new alliance between Concentric Network, a NEXTLINK Communications Company (NASDAQ: NXLK), and OpenAir will enable both companies to share resources and therefore strengthen and streamline business services offered to small and medium-sized businesses. OpenAir is the recognized leader in Web-native time billing and expense management. Concentric (www.concentric.com) is the leading provider of e-business solutions for growing companies.

OpenAir will be integrated into the registration process on Concentric's small business portal, "Gateway," which will allow users powerful new solutions for structuring their outsourcing of business tasks. Concentric Gateway is a business solutions center which aggregates services and applications that address a specific company need, allowing small- and medium-sized companies to grow, manage and outsource as their needs scale. The addition of OpenAir enables companies to streamline business processes, thereby improving overall efficiencies.

"OpenAir is looking forward to our new partnership with Concentric and being a part of their registration process," said Bill O'Farrell, CEO and founder of OpenAir. "OpenAir will now be able to offer our users Web-hosting and DSL capabilities on the OpenAir Web site through Concentric."

"We are pleased about leveraging the OpenAir unique business solution on our Concentric Gateway," said Connie DeWitt small/medium business marketing for Concentric. "We have pulled together a collection of solutions and applications that enable companies to efficiently and effectively manage their businesses via the Internet. The streamlining capabilities offered by OpenAir are an ideal complement to this strategy."

About OpenAir
OpenAir, founded in 1999 as Timebills.com, is a trusted Web-native platform of seamlessly integrated services that efficiently and economically streamlines business processes. These services allow professionals to build and submit proposals, analyze employee time, report and approve travel expenses online, track and bill time, create and deliver invoices, and outsource payroll and expense reimbursement.

More than 30,000 professionals currently utilize OpenAir to remove the frustration associated with common business tasks and drive revenue more efficiently.

Available 24 hours a day, seven days a week, OpenAir supports all major Internet browsers and is easily accessed from any Internet-equipped computer. All data is backed up on state-of-the-art servers, encrypted, password protected and only accessible to the OpenAir user.

About Conctentric
Concentric Network, an operating unit of NEXTLINK Communications, is a global provider of leading data and Internet services. Together with NEXTLINK, the company offers local and long distance voice, Digital Subscriber Line (DSL) access, Web hosting and e-commerce, Virtual Private Networks (VPNs), dedicated access, global transit and application infrastructure services for delivering applications over the Internet or a VPN.

NEXTLINK has assembled an unrivaled set of facilities-based broadband networks that, when complete, will serve much of the United States, Canada and Europe. In the United States, NEXTLINK has more than 410,000 metro fiber miles in operation and a 384,000 fiber-mile inter-city network under construction. The Company is also North America's largest holder of fixed broadband wireless spectrum, with licenses covering 95 percent of the population of the 30 largest U.S. cities and a partnership with licenses covering all of the top cities in Canada. NEXTLINK has also acquired more than 80,000 metro fiber miles in Europe to serve the London, Frankfurt, Brussels, Amsterdam and Paris markets. Additionally, NEXTLINK acquired an 88,000 pan-European fiber network connecting 21 major European cities and transatlantic capacity that will eventually expand to 10 Gbps.

Publicly traded NEXTLINK (NASDAQ:NXLK) is headquartered in McLean, Virginia and Concentric is located in San Jose, California. For more information visit www.NEXTLINK.com or www.concentric.net or contact Public Relations at publicrelations@concentric.com.

Contact
Jeff Hunt
OpenAir
Phone: 617-351-0230
jeffhunt@openair.com