The Airbus A310-300 is almost similar A310-200, but adds extra range with its increased MTOW. This enables the plane to carry extra fuel without sacrificing passengers, thus improving the range. There is an -300 variant that can change between cargo and passengers by removing the seating. A fuel distribution system controlled by a computer moves fuel to change the plane's center of gravity. A310 on Wikipedia Manufacturer's site
KLM 3TENS: Intra-european Widebodies - YESTERDAY'S AIRLINES
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KLM 3TENS: Intra-european Widebodies - YESTERDAY'S AIRLINES