Contingency fuel is carried to account for additional enroute fuel consumption caused by wind, routing changes or ATM: ATM/CNS restrictions.

Density altitude is pressure altitude corrected for temperature.

Pressure altitude is the indicated altitude when an altimeter is set to 29.92 (1,013.2 mb).

At FL260

To be the most efficient, aircraft descend at Vmd. Vmd increases with Weight, and therefore the rate of descent increases as well with weight.

Their formation is most often triggered by freezing water vapour from the exhaust of aircraft engines.

Glideslope: 329.15-335Mhz UHF 8 degrees either side, 10NM

Localiser: 108.10-111.95Mhz VHF 35 degrees either side, 17NM

The angle between between the chord line and the aircraft's longitudinal axis. It's a fixed angle for wings, but variable for variable incidence tailplanes.

Flying at Vmd. At this speed the aircraft is flying at the maximum ratio of Lift and Drag, maximizing the potential energy consumption in terms of distance travelled.

An adymensional number relating the lift with the dynamic pressure of the incoming flow. It is dependent on the form of the object and the angle of attack.

The point during a flight at which an aircraft is no longer capable of returning to the airfield from which it took off due to fuel considerations.

Beyond this point the aircraft must proceed to some other destination.