Modern Transportation

Modern transportation describes the various extremly modern vahicles found in the first two Ultimas. They can only be explained with the twisting of the time-stream, as they partially employ technology even newer than what currently is available on Earth.

Shuttle

The shuttle is the only spaceship capable of starting off and landing on the planet in Ultima I. Surprisingly, it is rather trivial to buy a shuttle, but it is deadly to use one, if you aren't wearing a Reflect Armour. Note that the shuttle has no weapons at all and therefore an ongoing spce ace has to switch to a different craft, once in space.

Air Car

This vehicle is a lot like a landspeeder from Star Wars. It hovers over the ground and has no trouble with land or water, but can't pass forests. Additionally, it is armed and can't shoot enemies at a distance. The air car was found in Ultima I and could be bought.

Bi-Plane

A bi-plane is a real, existing airplane. In Ultima II, it is capable of flying over all kind of terrian if launched. But could only fly in one direction while launched. If not flying, it is capable of rolling over grassland. Be warned that the plane can only land on grass, not forests or water. And it will outright crash into mountains, if a landing is tried there.

Bi-Planes could only be found in 1990 A.D. in New San Antonio and 2112 A.D. Aftermath in Pirate Harbour, though some also exist on the outer planets, especially Pluto. To actually be able to use a plane, one needs a skull key and a brass button.

Rocket

Space rockets are in Ultima II only available in the Aftermath town Pirate Harbour. To operate one after stealing it from the communists, a Reflect or Power Armour is absolutely needed, as well as an ankh to start it and Tri-Lithium to fuel it. Once in space, a set of three coordinats (XYZ) have to be entered to engage a hyperwarp to the target, using one Tri-Lithium.

Landing is much more tricky. The rocket needs to land on grass, or it'll explode. And should there be no Tri-Lithium left, it is death.

Real Reason
The real reason behind this bizarre mix of medival scenario and modern or sci-fi technology was, that at the beginning, Richard Garriott hadn't decided what direction he should take the series. After Ultima II, he'd decided to drop the sci-fi stuff, and the story got more mature.