A refuelling system suitable for use with an overwing fuelled aircraft comprising: (a) a fuel storage vessel capable of storing aircraft fuel; (b) a stored fuel grade identification means for identifying the fuel grade stored in the fuel storage vessel and available type(s) of delivery of the fuel to the aircraft; (c) a fuel dispensing system fluidly connected to the fuel storage vessel comprising a means of delivering fuel to an overwing fuelled aircraft and a mechanism that permits or prevents the dispensing of the stored aircraft fuel; (d) an aircraft fuel grade identification means being attached to, or forming part of, an overwing fuelled aircraft, wherein said aircraft fuel grade identification means represents the fuel grade requirement of the aircraft and is readable from the exterior of the aircraft; (e) a hand-held device comprising a means for reading the aircraft fuel grade identification means; (f) a computer interface where the aircraft registration number can be inputted; (g) a transmission and receiving system which enables information regarding the fuel grade that had previously been supplied to the aircraft having the aircraft registration number inputted into the computer interface and the type of delivery of fuel which may be used by said aircraft to be retrieved from a remote database; (h) optionally, a customer identification system which comprises a customer identification card and/or number, and a processing system which comprises a transmission and receiving system, wherein the customer identification system is capable of obtaining at least the customer name and the fuel grade from the customer identification card and/or a database entry associated with the customer identification number; (i) an automated cross-check system which is configured to retrieve the fuel grades identified by the fuel identification means in (b), retrieve the fuel grade identified in (d) from the hand-held device, retrieve the type(s) of delivery of fuel identified by the fuel identification means in (b) and by the system of element (g), and the previous fuel grade supplied to the aircraft identified by the system in element (g) and optionally also in element (h), which can generate a positive response signal if all of the fuel grades identified are compatible with each other and the type(s) of delivery of fuel to the aircraft are compatible; and (j) a signal processing system which can process the positive response signal generated by the automated cross-check system, which signal processing system interfaces with the mechanism that permits or prevents the dispensing of aircraft fuel through the fuel dispensing system and will allow the refuelling to proceed if the automated cross-check system generates a positive signal. (a) a fuel storage vessel capable of storing aircraft fuel; (b) a stored fuel grade identification means for identifying the fuel grade stored in the fuel storage vessel and available type(s) of delivery of the fuel to the aircraft; (c) a fuel dispensing system fluidly connected to the fuel storage vessel comprising a means of delivering fuel to an overwing fuelled aircraft and a mechanism that permits or prevents the dispensing of the stored aircraft fuel; (d) an aircraft fuel grade identification means being attached to, or forming part of, an overwing fuelled aircraft, wherein said aircraft fuel grade identification means represents the fuel grade requirement of the aircraft and is readable from the exterior of the aircraft; (e) a hand-held device comprising a means for reading the aircraft fuel grade identification means; (f) a computer interface where the aircraft registration number can be inputted; (g) a transmission and receiving system which enables information regarding the fuel grade that had previously been supplied to the aircraft having the aircraft registration number inputted into the computer interface and the type of delivery of fuel which may be used by said aircraft to be retrieved from a remote database; (h) optionally, a customer identification system which comprises a customer identification card and/or number, and a processing system which comprises a transmission and receiving system, wherein the customer identification system is capable of obtaining at least the customer name and the fuel grade from the customer identification card and/or a database entry associated with the customer identification number; (i) an automated cross-check system which is configured to retrieve the fuel grades identified by the fuel identification means in (b), retrieve the fuel grade identified in (d) from the hand-held device, retrieve the type(s) of delivery of fuel identified by the fuel identification means in (b) and by the system of element (g), and the previous fuel grade supplied to the aircraft identified by the system in element (g) and optionally also in element (h), which can generate a positive response signal if all of the fuel grades identified are compatible with each other and the type(s) of delivery of fuel to the aircraft are compatible; and (j) a signal processing system which can process the positive response signal generated by the automated cross-check system, which signal processing system interfaces with the mechanism that permits or prevents the dispensing of aircraft fuel through the fuel dispensing system and will allow the refuelling to proceed if the automated cross-check system generates a positive signal.