Conformal fuel tanks are additional fuel tanks fitted closely to the profile of an aircraft which extend either the range or "time on station" of the aircraft, with a reduced aerodynamic penalty compared to external drop tank

Drop tank

In aeronautics, a drop tank is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable...

s.

Conformal fuel tanks have the disadvantage that, unlike drop tanks, they cannot be discarded in flight. This is because conformal tanks are plumbed

Plumbing

Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...

 into the aircraft, and can only be removed on the ground. Thus, when the CFTs are empty, the aircraft continues to suffer the same aerodynamic penalty, with no benefit. However, to use the Eurofighter Typhoon

Eurofighter Typhoon

The Eurofighter Typhoon is a twin-engine, canard-delta wing, multirole combat aircraft, designed and built by a consortium of three companies: EADS, Alenia Aeronautica and BAE Systems; working through a holding company, Eurofighter GmbH, which was formed in 1986...

 as an example, an aircraft with CFTs can carry a full weapons load and two 1,500 litre CFTs, whereas a Typhoon without CFTs has to sacrifice at least two weapons pylons to carry drop tanks, reducing either range or weapons load.

CFTs also have the advantages of not significantly increasing an aircraft's radar cross-section

Radar cross section

Radar cross section is a measure of how detectable an object is with a radar. A larger RCS indicates that an object is more easily detected.An object reflects a limited amount of radar energy...

, and allowing a higher maximum speed than drop tanks.

Conformal fuel tanks

• F-15C Eagle/F-15E Strike Eagle

F-15C entered service with CFT capability. Initially known as FAST packs (Fuel And Sensor Tactical), each unit carried an additional 849 gal of fuel and were first tested on the F-15B in 1974. Today only Israeli F-15C/Ds regularly use CFT's. All U.S. F-15Es, and Strike Eagle export variants such as the IAF and Singapore models, are fitted with CFT's and require modification to fly without them. The FAST pack was originally intended to carry a navigational and targeting infrared sensor system (thus "Fuel And Sensor"); however, the F-15 simply began carrying LANTIRN

LANTIRN

Low Altitude Navigation and Targeting Infrared for Night, or LANTIRN, is a combined navigation and targeting pod system for use on the USAF's premier fighter aircraft — the F-15E Strike Eagle and F-16 Fighting Falcon...

 pods for ground-attack missions instead.

• F-16C/D Block 50/52+, F-16E/F Block 60 and F-16I Sufa
  F-16 Fighting Falcon variants
  A large number of F-16 Fighting Falcon variants have been produced by General Dynamics, Lockheed Martin, and various licensed manufacturers. The details of the F-16 variants, along with major modification programs and derivative designs significantly influenced by the F-16, are described...
  
  

Export aircraft for Greece, Israel, Poland, Turkey, Singapore,Morocco and the UAE all plumbed for carriage of two CFTs, each capable of holding 450 gal

• Dassault Rafale
  Dassault Rafale
  The Dassault Rafale is a French twin-engine delta-wing multi-role jet fighter aircraft designed and built by Dassault Aviation. Introduced in 2000, the Rafale is being produced both for land-based use with the French Air Force and for carrier-based operations with the French Navy...
  
  

Two 1150 litre CFTs were first tested by Dassault in April 2001.

• Eurofighter Typhoon
  Eurofighter Typhoon
  The Eurofighter Typhoon is a twin-engine, canard-delta wing, multirole combat aircraft, designed and built by a consortium of three companies: EADS, Alenia Aeronautica and BAE Systems; working through a holding company, Eurofighter GmbH, which was formed in 1986...
  
  

Wind tunnel tested by BAE, two CFTs with 1500 litre capacity.

• AIDC F-CK-1 Ching-kuo

The F-CK-1D prototype ("Brave Hawk") and the F-CK-1C single-seater prototype are equipped with the new CFTs.

Distended internal tanks

• English Electric Lightning
  English Electric Lightning
  The English Electric Lightning is a supersonic jet fighter aircraft of the Cold War era, noted for its great speed and unpainted natural metal exterior finish. It is the only all-British Mach 2 fighter aircraft. The aircraft was renowned for its capabilities as an interceptor; Royal Air Force ...
  
  
• Gloster Javelin
  Gloster Javelin
  The Gloster Javelin was an "all-weather" interceptor aircraft that served with Britain's Royal Air Force in the late 1950s and most of the 1960s...
  
  
• Gloster Meteor
  Gloster Meteor
  The Gloster Meteor was the first British jet fighter and the Allies' first operational jet. It first flew in 1943 and commenced operations on 27 July 1944 with 616 Squadron of the Royal Air Force...
  
  
• Shenyang J-6
  Shenyang J-6
  The Shenyang J-6 was the Chinese-built version of the Soviet MiG-19 'Farmer' fighter aircraft.-Design and development:...
  
  
• Q-5 Fantan