Surprisingly, the Boeing 707-320 has not been similarly modernised; the last of more than 900 Boeing 707/720s built (excluding military E-3s) is shown taking off in March 1982.

Another older airframe adapted to take advantage of the CFM56, although only as a conversion, is the McDonnell Douglas DC-8. This Series 72 with four CFM56-2s benefits from a dramatic increase in fuel efficiency.

The General Electric CF6, in its -80C2 version, will become available in June 1985 with ratings of up to 62,000 lb st (28 123 kgp). The Airbus A300-600 (photo) is among the transports it will power.

The Rolls-Royce RB.211-535E4 challenges the PW2037 on the Boeing 757. This is the latest variant in this unique family of three-spool engines; the earlier RB.211-535C is used in the Monarch 757.

Basically a refanned Spey, but with many other less obvious changes too, the Rolls-Royce Tay is now being tested and should fly in 1986 in the Fokker F100 airliner (photo) and later in the Gulfstream IV long-range business jet.

The Pratt & Whitney JT8D-209 is a refanned version of the JT8D. It has been used successfully on the McDonnell Douglas MD-80 airliner (on photo) since 1979, and has contributed to the continuing success of this family of variants derived from the DC-9.

The Boeing 737-300 has CFM56-3 engines where the smaller-diameter JT8Ds were originally fitted. To make this possible, the nacelle has been designed to accommodate the engine accessories on either side of the fan casing, and with a flattened intake to give sufficient ground clearance.