UFOs

In other languages: 한국어.

The UFOs seen in the skies of UFO: Enemy Unknown 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 a 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 temporarily. In the long run, it will actually further antagonise them, causing the aliens to accelerate their agendas. In any case, captured alien technology is essential to our research and finances.

Alien Subs are the equivalent in Terror from the Deep. The third game in the series, Apocalypse, introduced another fleet.

UFO Interiors

The core components of a UFO are UFO Navigation, UFO Power Source, Alien Alloys, and Elerium-115. You will recover less from crashed UFOs, but sometimes it's critical to shoot them down. Larger UFOs may contain additional 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 transportation 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	Accel.	Weap. Power	Weap. Range*	Damage Cap.	Crashed Pnt.	Destroyed Pnt.
Small Scout	Very Small	2,200	12	0	0	50	50	100
Medium Scout	Small	2,400	9	20	15	200	75	150
Large Scout	Small	2,700	9	20	34	250	125	250
Abductor	Medium	4,300	8	40	22	500	250	500
Harvester	Medium	4,000	8	40	20	500	250	500
Supply Ship	Large	3,200	6	60	36	2,200	400	800
Terror Ship	Large	4,800	6	120	42	1,200	500	1,000
Battleship	Very Large	5,000	6	148	65	3,200	700	1,400

* The figures given in the in-game UFOpaedia are a factor of 8 too high, relative to Craft Armament ranges. The range given for the Supply Ship is also incorrect in the in-game UFOpaedia. * It is impossible to destroy the Supply Ship, Terror Ship and Battleship.

Weapons vs. UFOs

Since rearming your aircraft every time you spot a different UFO takes too long, you must decide on a standard weapon configuration, unless you want to maintain multiple aircraft in different weapon configurations, which would be overly expensive and inefficient. So, in effect, there is only really one way to go:

Before you can fully equip your ships with Plasma Beams: Use Stingray Missiles against Very Small UFOs, to have some chance of not totally destroying them. Use dual Avalanche Missiles against Small or Medium enemies. Use at least 2 interceptors with dual Avalanche Missiles against Terror Ships. Do not attempt to shoot down Supply Ships or Battleships unless it is unavoidable (e.g. to protect an undefended main base).

Thereafter: Use Plasma Beams on everything, except Battleships. Only a single Plasma Beam is necessary, except against Battleships. Do not engage Battleships until you have several advanced aircraft (or enough Fusion Ball Launchers to fully arm 4 Interceptors). Always engage Battleships with as many aircraft as possible, to split the enemy fire. Once you have several Firestorms and Avengers, you can start to shoot down Battleships with Plasma Beams... but if your soldiers are strong enough, it's usually more profitable just to let them land undamaged, so you can take more of their loot in ground combat.

With a Plasma Beam you will always have stand off range advantage against anything short of a Battleship, making dual Plasma Beams unnecessary. So there is an argument for mounting one Plasma Beam and (optionally) one Fusion Ball Launcher. The FBL gives extra firepower in a Battleship fight. However it means routine engagements will be much more costly because of the high expense of the Fusion Ball ammo. Fitting one or two FBLs might be advisable if Battleships are expected imminently, e.g. if Retaliation mission patterns have been detected.

Trivia

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. If you want to be able to do a Recovery mission against the Small Scout, don't use Avalanches - use Cannon, Laser Cannon or Stingray only. Only the Cannon will guarantee not to totally destroy the Small Scout. Stingray or Laser Cannon have a 57% (20/35) chance to destroy it.
• 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 candidates for UFO Ground Assaults.
• Avalanches or Plasma Beams should be used against Large Scouts due to that UFO's weapon range of 34km.
• Avalanches can be used against Terror Ships, although at least two craft must be sent since you need to do 600 damage to force it to crash land.
• Laser Cannons, with a range of 21km, can be safely used against Medium Scouts and Harvesters. However, Avalanche-armed craft are of use against a larger variety of craft and Plasma Beams, once they become available, are superior in every regard.
• Plasma Beams can safely be used (even by Interceptors) against any UFOs except Battleships.
• It's possible to down a Battleship with only 3 craft using Fusion Ball Launchers, if they all survive UFO fire long enough to fire all charges. But if you lose a craft and then are even moderately unlucky with damage dealt, the interception will fail. With only 2 FBL-armed craft you would need a lot of luck - superhuman luck if the craft are Interceptors.
• When attacking a Battleship with Interceptors, Fusion Ball Launchers are safer than Plasma Beams. Attacking with 4 aircraft, on Beginner Level, you would expect to lose one Interceptor if armed with FBLs, versus 2 lost Interceptors armed with Plasma Beams. This is because the FBLs kill the Battleship faster, and with less time spent taking fire but not returning it. The exercise is expensive in terms of ammunition, but cheaper than losing an extra Interceptor and its armament.

Interceptors Vs. UFOs

• The Interceptor is slow compared to UFOs, so any alien craft it is chasing must slow down. The "sluggish" Small Scout can outrun it!
• The Firestorm can handily intercept all UFOs except the Harvester, Terror Ship, and Battleship, which must be going lower than top speed for the Firestorm to catch up.
• The Lightning can be outrun by the Harvester, Abductor, Terror Ship, Battleship, and Supply Ship.
• The Avenger can hunt down and attack any UFO in the game easily, due to its massive speed.

UFO Behavior

Aliens in their UFOs will behave in a different manner depending on what sort of mission they are tasked. All currently available data is summarized in the following points. UFOs will ALWAYS head to their mission locale (as listed in the Hyper-Wave Decoder information) at top speed and then initiate one of the following behaviors depending on the mission:

• Most UFOs will slow down continuously as they prepare to land. Check the altitude to try and guess when and where they're going to land so you can do a UFO Ground Assault.
• Certain missions are done by several ships instead of just one. These are Alien Base and Alien Infiltration missions.
• Alien Research mission UFOs will slow down significantly and do several slow sweeps as they probe for data, also landing for brief periods.
• Alien Harvest and Alien Abduction missions will sweep an area at moderate speed and land multiple times as they locate and abduct cattle and humans.
• Alien Infiltration ships will land in the cities, in the country they are attempting to infiltrate. Scouts of various sizes will appear and maybe land. Later, they will send Supply Ships, Battleships, and Terror Ships in an attempt to bribe and scare the country's leaders into submission. X-COM will lose funding from this country and an Alien Base will appear if the mission is successful.
• Alien Retaliation ships will scout a specific area where they have been having trouble, in a manner similar to an Alien Research mission. If your base is nearby, shoot the UFO down. Once an X-COM base is located, the aliens will send a Battleship directly at it at top speed, low in the atmosphere.
• Alien Base missions will behave in much the same manner as Alien Research. When constructing the Alien base, a fleet of Supply Ships and Battleships will land often as they search for a suitable location. One Battleship, two supply ships, and three Large Scouts is common.
• Supply Ships on an Alien Supply mission will be dispatched at exactly 00:30 and will land only once, directly on top of the base. Supply ships on this type of mission will run at full speed their entire time, not even slowing down as they land. They only stay on the ground a short time, so advanced craft are needed to deal with them if they are airbourne.
• Alien Terror UFOs will slowly meander about looking for a city for the Terror Ships to land at. If the scouts are shot down, the first Terror Ship will behave much like the scouting UFOs. It may iniitiate a terror mission, although rare. If the scouts are not shot down, the Terror Ship will arrive in the region, slow down to pick a city, and then land. The possible second Terror Ship (if you forced the Aliens to scout with a Terror Ship) will pick a city and then land, regardless.
• If you are successful at preventing lesser UFOs from doing their jobs, the aliens will eventually send Battleships to do the dirty work, hoping you won't be able to attack them. (They will not participate in Alien Research and Alien Terror missions, though.)