A starport doesn't get a Class A or B rating unless it is capable of performing annual maintenance on ships of all tech levels.
For once, I'm in agreement with Hans.
Otherwise, TL 15 vessels would have a real hard time operating on the Imperial Fringe.
Another thing to consider.... The neat TL rules that DGP introduced. You can find them in Grand Survey, and the rules were carried on into MT's World Builder's Handbook.
Basically, what DGP did was add more detail to the world TL ratings. The TL in the UWP was still the main, overall TL used, but as a general rating. Several categories of tech were broken down, with modifiers, to show a world's teck in certain areas.
For example, a desert world would have a very low tech in Water Transport even though the world general TL may be quite high. A world without an atmosphere might have a low TL in that area even though the UWP rating is higher.
The DGP rules also go into TL for installations. Like the US bases in Vietnam in the 70's, sometimes you have a high tech installation surrounded by a very low tech environment. So, Naval Bases, for example, all have minimum TLs, no matter the TL of the world the base sits upon. The same goes for Starports. Each class of starport as a minimum TL for that installation.
For example, Pysadi, in the Aramis subsector of the Spinward Marches is a TL 4 world, but it also sports a Class C Starport. Under the DGP rules, the Starport would be a minimum TL 8 (and could be higher under certain circumstances).
Don't forget to make some assumptions as a GM based on the info you have about the worlds. Common Sense is your friend.
In one of the campaigns I ran a few years ago, I used these worlds as possible homeworlds for the PCs.
Pysadi C4766D7-4 Agricultural. Non-industrial. Gas Giant in system. Imperiallines Station.
Vanejen C686854-5 Rich. Imperial Research Station.
Natoko B582211-8 Imperial Naval Base. Non-industrial. Low Pop. Gas Giant in system. Naasirka Stationl Tukera Station.
Patinir C000632-9 Asteroid Belt. Gas Giant in system. Imperiallines Station. Non-agricultural. Ancient Site.
Aramis A6B0556-B Imperial Naval Base. Imperial Scout Base. Non-industrial. Subsector Capital. Akerut Station. Tukera Station. Naasirka Station. Desert World.
A GM can make a lot of TL assumptions just based on that information. Aramis, the desert world, probably has really low tech flyers (if any at all). Natoko has a low population, so most of the world is not developed. At that low pop, the people must be in the installations alone. This will affect tech. Patinir, an asteroid belt, again, has certain Common Sense effects on technology available in the area.
In that campaign, I would take the info I had and make these little write-ups for the players, handing them to the player who had a character from that world so that the player would have a sense of where his character had come from.
For example, if a player's character hailed from Pysadi, I'd hand him this short write up:
HOMEWORLD PYSADI
Pysadi, a world in the Aramis scatters, lies in a hot binary system. People live close to the poles, and the natives tend to be weak because of the 0.5G local gravity. The atmosphere is dirtied with a light taint.
Pysadi is a low-tech world settled by a Solomani muslim sect a few hundred years ago. Characters from Pysadi are considered to be Imperials, not locals, who live and operate the Class C downport and its associated businesses (not unlike working for an oil company in the Middle East today). The entire interior environs of the starport are built using standard 1G grav plates (typical of space station construction), and although Pysaid sports a TL 4, the starport is considered TL 8.
Typical temperatures (degrees F) on Pysaidi average 171 at the equator (Summer 174 - Winter 154) because of the binary stars. The tropics aren't much better, averaging 144 (Summer 154 - Winter 117), but the habital area of Pysadi, the two poles, are fairly comfortable, averaging 81 (Summer 109 - Winter 25).
Pysadi is ruled by a fairly strict Religious Dictatorship, but the downport is considered extra-territorial. The Class C instellation sees moderate traffic from free traders operating in the scatters, and Imperriallines maintains on office on the world.
Over the last five years, the Imperium has built and maintains a small scientific outstation in the Pysadi system, deep in the outer orbit of one of the system's stars.
PYSADI
STARPORT: C
SIZE: Small
ATMOSPHERE: Std. Taint
HYDROSPHERE: Wet
POPULATION: Moderate
LAW LEVEL: Moderate
TECH LEVEL: Industrial
(post continued)