• Flexible (if transparent transponders)
• Easy to install new circuits
• Circuit costs independent of distance
• Broadcast possibilities
• Temporary applications (restoration)
• Niche applications
• Mobile applications (especially "fill-in")
• Terrestrial network "by-pass"
• Provision of service to remote or underdeveloped areas
• User has control over own network
• 1-for-N multipoint standby possibilities

Disadvantages

• Large up front capital costs (space segment and launch)
• Terrestrial break even distance expanding (now approx. size of Europe)
• Interference and propagation
• Congestion of frequencies and orbit

• When the unique features of satellite communications make it attractive
• When the costs are lower than terrestrial routing
• When it is the only solution

Examples:

• Communications to ships and aircraft (especially safety communications)
• TV services - contribution links, direct to cable head, direct to home, SNG
• Data services - private networks
• Overload traffic
• Delaying terrestrial investments
• 1-for-N diversity
• Special events

When to use terrestrial:

• PSTN - satellite is becoming increasingly uneconomic for most trunk telephony routes
• but, there are still good reasons to use satellites for telephony such as: thin routes, diversity, very long distance traffic and remote locations.
• Land mobile/personal communications - in urban areas of developed countries new terrestrial infrastructure is likely to dominate (e.g. GSM, FLMPTS)
• but, satellite can provide fill-in as terrestrial networks are implemented, also provide similar services in rural areas and underdeveloped countries