The Boeing C-137 Stratoliner is a retired VIP transport aircraft derived from the Boeing 707 jet airliner used by the United States Air Force.
Other nations also bought both new and used 707s for military service, primarily as VIP or tanker transports.
In addition, the 707 served as the basis for several specialized versions, such as the E-3 Sentry AWACS aircraft.
The designation C-18 covers several later variants based on the 707-320B/C series.
The C-137 should not be confused with the superficially-similar Boeing C-135 Stratolifter, although they share a common ancestor the two aircraft have different fuselages.
Variants
C-18
The C-18 is the US military designation for the conversions of the 707-320B series.
C-18A
Eight second-hand 707-323Cs bought as crew trainers for the EC-18Bs, four later converted to EC-18B, two converted to EC-18D, one to C-18B, one was not taken into service and was used for spares.
C-18B
One C-18A modified with instrumentation and equipment to support the Military Strategic and Tactical Relay System (MILSTAR).
EC-18B
Four C-18As modified alongside examples of the C-135 for Advanced Range Instrumentation Aircraft (ARIA) missions in support of the Apollo space program.
The designation E-7 was originally applied to modified Boeing 707s before being replaced by the EC-18 designation.
EC-18C
Original designation for two prototype J-STAR aircraft, later redesignated E-8A.
EC-18D
Two C-18As modified as a Cruise Missile Mission Control Aircraft (CMMCA).
TC-18E
Two second-hand 707-331 aircraft modified for E-3 pilot and crew training.
TC-18F
Two second-hand 707-382 aircraft modified for E-6 pilot training.
VC-137A
Three 707-153s with a 22-passenger VIP interior and provision for use as an airborne command post, re-designated VC-137B.
VC-137B
The three VC-137As re-engined with four Pratt & Whitney JT3D-3 engines, operated by the 89th Military Airlift Wing, redesignated C-137B.
C-137B
The three VC-137Bs redesignated when downgraded from VIP role.
VC-137C
Two 707-353Bs were purchased by the USAF for service as presidential transports with call signs SAM 26000 and SAM 27000, later redesignated C-137C.
C-137C
The two VC-137Cs were redesignated when downgraded from presidential use.
SAM 26000 and SAM 27000 were retired in 1998 and 2001 respectively.
Two further C-137Cs were acquired by the USAF on 24 March 1988, one 707-396C and one 707-382B bought second hand in 1987.
EC-137D
Two aircraft built as Early Warning and Control System prototypes.
Later re-engined and re-designated E-3A.
A further second-hand 707-355C aircraft was acquired and configured as an airborne special operations command post.
CC-137 Husky
Canadian Forces designation for the 707-347C.
Five were purchased new in 1970.
KC-137
Brazilian Air Force
707
IRIAF operates 707 Tankers and Transports.
707 Re’em
The Israeli Air Force operates an undisclosed number of converted Boeing 707s with flying booms in 120 Squadron.
Israel’s fleet are former civilian aircraft adapted for military uses such as aerial refueling of fighter jets and transport.
Able to carry 20 extra fuel tanks while modified for aerial refueling, the Re’ems can be adapted to carry passengers as well as cargo such as military equipment and ammunition.
707T/T
The 707 Tanker/Transport.
Italy purchased and converted four 707s, two to tankers and two to a straight freighter.
Omega Aerial Refuelling Services also operates K707 tankers for lease.
KE-3A
The Royal Saudi Air Force purchased eight E-3 airframes configured as aerial refueling tankers.
Condor
Airborne Early Warning, Command and Control aircraft developed in conjunction with Israel Aircraft Industries using a former Lan Chile aircraft.
CT-49A/707TCA
Three ex-Sabena airliners converted to TCA (Trainer Cargo Aircraft) in 1989 to support the NATO NAEWF E-3A training and air transport/cargo based on Boeing 707-320B.
The aircraft were capable of making dry hook ups with the USAF Flying Boom air-to-air refuelling system for training of pilots that were new to NAEWF, but also served as cargo/passenger transport.
The two oldest/highest time 707s were replaced by two former Luftwaffe 707s in 1999.
