From the back of the book:
From routine operations to dealings with officialdom, the starports of worlds in and out of the Imperium are important places of business for starship crews and other travellers. Brokers with cargo, port officers imposing legal requirements, technicians, crewmen, tourists... a whole subculture exists within the bounds of the starport extrality fence. Whether they are seeking business or pleasure, information or goods, rumors or jobs, travellers will find them among teh landing pads and control towers of the planetary starports.
Starport Planetfall is a collection of detailed encounter tables designed to generate random encounter situations for Traveller. From the largest planetary starport to the smallest landing fields, tables and encounter descriptions give depth and detail even to innocent encounters that may have no bearing on the adventure or campaign in progress... but provide flavor, atmosphere, distractions, or even whole new adventures that will serve the Traveller referee in good stead.