UFOs

The UFOs seen in the skies are big, blocky, geometric shapes that lack any form of aerodynamics. They are able to fly at breakneck speeds through the power of Elerium-115 and the resiliency of Alien Alloys. UFOs come in a variety of forms ranging from the tiny Small Scouts right up to the massive Battleships.

UFOs are the aliens' sole method to get to Earth, so in theory, it would be possible to halt the alien advance if X-COM could maintain absolute air superiority. Earth's forces do not initially have the resources required for such a task, and even if it becomes possible, the aliens have an vast resource supply and will not be set back by a war of attrition. In addition, alien undercover agents will continue to erode Earth's defenses from the inside.

Despite this, commanders should still shoot down as many UFOs as possible. At the very least, it may slow the aliens down some.

UFO Interiors

The core components of a UFO are UFO Navigation, UFO Power Source, Alien Alloys, and Elerium-115. Some larger UFOs, however, contain other equipment such as Alien Surgery, Alien Food, Examination Rooms, and even Alien Entertainment.

UFO hulls and interiors are composed of Alien Alloys. This provides incredibly light, yet strong, armour - perfect for spacecraft construction. The only field weapons able to punch the outer shell of a UFO are Blaster Launchers. The interior of UFOs are also very strong, but made of much thinner alloys that can be destroyed by repeated fire from Heavy Plasmas, the Tank/Laser Cannon, Hovertank/Plasma not to mention the Blaster.

Great care should be taken when clearing out a UFO. The interiors of larger UFOs are often deadly mazes, with tight corridors, and sharp corners, and choke points that even a single alien can defend. An inexperienced squad leader will also often face dead ends, or encounter treacherous storage rooms - most of the time these are empty, yet occasionally an alien will hide in them to ambush your soldiers. Two UFOs even have trapdoors - the Terror Ship and the Harvester, which the aliens frequently use.

Squad leaders should also use explosives wisely. A stray explosion may accidentally damage precious Elerium-115 or set off secondary reactions. The low ceilings also limit the range of Grenades. The tight spaces do, however, make Proximity Grenades particularly useful, and grenade explosions can go around corners to hit aliens lying in wait.

UFO Types

The UFOs deployed by the aliens range in size and the mission profiles they are most commonly seen on, some are also much more common to certain of the alien races encountered.

Very Small UFOs

Small Scout - Very Small UFO that looks like an Apollo capsule. Primarily used for research.

Small UFOs

Medium Scout - The classic 'flying-saucer' craft. Able to fill a variety of roles.

Large Scout - Cross-shaped UFO, slightly larger than the Medium Scout. Very versatile.

Medium UFOs

Abductor - Medium-sized UFO used primarily by Sectoids and Floaters for human experimentation.

Harvester - Medium-sized UFO with food and surgery units. Used to abduct cattle for food. Usually crewed by Floaters.

Large UFOs

Supply Ship - Large-sized UFO for tranportation of aliens, food, and other supplies.

Terror Ship - Large UFO used to unleash assault teams and Terror Units on residential areas.

Very Large UFOs

Battleship - Very Large UFO used to intimidate Earth's peoples and leaders, and to assault X-COM bases, along with a variety of other roles.

Quick Comparision Table

Craft	Size	Max Speed	Weapon Power	Weapon Range*	Damage Capacity
Small Scout	Very Small	2,200	0	0	50
Medium Scout	Small	2,400	20	15	200
Large Scout	Small	2,700	20	34	250
Abductor	Medium	4,000	40	22	500
Harvester	Medium	4,300	40	20	500
Supply Ship	Large	3,200	60	28.5	2,200
Terror Ship	Large	4,800	120	42	1,200
Battleship	Very Large	5,000	148	65	3,200

* The figures given in the in-game UFOpaedia are a factor of 8 too high, relative to Craft Armament ranges.

Weapons vs. UFOs

Comparing the weapon range and damage capacity of UFOs to the range and damage of Craft Armaments, one can discern that:

• Any weapon, even the lowly Cannon, can be used against Small Scouts, since they can't shoot back.
• Stingrays, with a range of 30km, are completely safe to use against Medium scouts, and can even be used to safely down Abductors and Harvesters. They can also be used to attack Supply Ships, although you need to attack with at least three craft in order to do enough damage to down the UFO. Furthermore, Supply Ships usually travel faster than Interceptors and always land, making them better candiates for UFO Ground Assaults.
• Avalanches or Plasma Beams should be used against Large Scouts due to their weapon range of 34km.
• Avalanches can be used against Terror Ships, although at least two craft must be sent. Although it would seem that all 12 missiles carried (6 on each craft) would need to hit to down a Terror Ship (1200 damage), in practice 4 salvos (8 missiles) are usually enough. However, occasionally one salvo will miss, necessitating 5 or more salvos. Because of the last shot out of range bug, in order to hit a Terror Ship with all your Avalanches, you should briefly switch to Aggressive mode while each craft's last salvo is in flight.
• Laser Cannons, with a range of 35km, can be safely used against all UFOs except Terror Ships and Battleships. However, the Plasma beam is superior in every regard, once it is available to you.
• Plasma Beams can safely be used (even by Interceptors) against any UFOs except Battleships. Even against Battleships, Plasma Beams are better than Fusion Ball Launchers because a minimum of four Fusion Ball-armed craft are required to down a Battleship.