Inmarsat Receives Phase 2 Notice From LightSquared

LONDON, January 28, 2011 - Inmarsat plc (LSE: ISAT.L), the leading provider of global
mobile satellite communications services, today announced that it has
received notice from LightSquared triggering Phase 2 of the Cooperation
Agreement between Inmarsat and LightSquared.

Under Phase 2 of the Cooperation Agreement Inmarsat will
support a spectrum plan that increases the total capacity available through
the LightSquared network. In return Inmarsat will immediately begin to
receive payments of US$115m per annum, payable quarterly in advance. Phase 2
of the Cooperation Agreement has an initial minimum commitment period of 5
years. In connection with the notice announced today, Inmarsat has received a
first partial quarterly payment of US$20.1m.

Perry Melton, Inmarsat's Chief Operating Officer said, "In
preparation for the notice received today, Inmarsat has already initiated
programmes to ensure our customers are protected from interference risks and
has conducted analysis of the issues over an extended period. Inmarsat is
confident that the effects on customers will be minimal and, where needed,
will be dealt with responsibly."

The notice for Phase 2 follows the notice given in August 2010 for Phase
1. Under Phase 1 Inmarsat and LightSquared agreed to a plan to enable the
re-banding and efficient reuse of L-band radio spectrum covering North
America. Phase 1, which is currently being implemented, is designed to
increase the contiguous spectrum available to support the deployment of 4G
ancillary terrestrial component ("ATC") services and to protect the continued
deployment and growth of MSS activities in North America.

About Inmarsat

Inmarsat plc (LSE: ISAT) is the leading provider of global
mobile satellite communications services. Since 1979, Inmarsat has been
providing reliable voice and high-speed data communications to governments,
enterprises and other organizations, with a range of services that can be
used on land, at sea or in the air. The company's services are delivered
through a global network of more than 400 distribution partners and service
providers operating in 100 countries. For the year ended 31 December 2009,
Inmarsat plc had total revenue of US$1,038.1m (2008: US$996.7m) with an
EBITDA of US$594.2m (2008: US$531.2m). For more information, please visit
www.inmarsat.com.

About LightSquared

LightSquared's mission is to revolutionize the U.S. wireless
industry. Through the creation of the first-ever wholesale-only nationwide
4G-LTE network complemented by satellite coverage, LightSquared offers people
the speed, value, and reliability of universal broadband connectivity,
wherever they are in the United States. Through its wholesale-only business
model, those without their own wireless network or who have limited
geographic coverage or spectrum can develop and sell their own devices,
applications, and services using LightSquared's open 4G network-at a
competitive cost and without retail competition from LightSquared. For
further information about LightSquared, please go to
www.LightSquared.com.

Contacts: Investor Enquiries: Simon Ailes, Inmarsat plc, Telephone: +44(0)20-7728-1518, Email: simon_ailes at inmarsat.com , Media Enquiries: Chris McLaughlin, Inmarsat plc, Telephone: +44-779-6276033, Email:christopher_mclaughlin at inmarsat.com