Due to the weak stray magnetic field affecting both the aircraft's navigation system and control signals, magnetic cargo is classified as Class 9 dangerous goods according to the International Air Transport Association (IATA) requirements and must be restricted during transportation. So now magnetic testing is required for some air cargo containing magnetic substances (such as speakers) to ensure the flight safety of the aircraft. Below is a brief introduction and explanation of the stray magnetic field testing and related requirements for air cargo. The main reference standards are: International Air Transport AssociationPackaging instruction 902State variations: AEG-01 FRG-09, USG-12 Operator Variations: AM-09, JL-06, KZ-04, VN-11 The limit requirements for stray magnetic fields are as follows: If the high magnetic field strength measured at a distance of 2.1m (7ft) from the tested object does not exceed 0.159A/m (200nt), the item is not restricted as a magnetic substance and can be transported as a general cargo. If the magnetic field strength at any point 4.6m from the surface of the assembled goods does not exceed 0.418A/m (0.00525gauss) or the deviation of the magnetic compass scale does not exceed 2 degrees, the goods can be transported as dangerous goods. If this requirement cannot be met, the goods cannot be transported by air, and the owner can entrust the goods to sea. Before magnetic testing, customers need to package the goods according to air transportation requirements. The testing process itself will not damage the packaging of the goods. When conducting magnetic field testing, the goods are not unpacked, but only stray magnetic field testing is performed on each side of each piece of goods. There are two specific detection methods that only need to meet any one of the testing methods: Method 1: Use a magnetic field measuring instrument (with a measurement unit of A/m, or gauss), first find two points in an area without any magnetic field other than the Earth's magnetic field, located in the east/west straight line m, make the magnetic field measuring instrument at one point and reset it to zero, and then place the measured magnetic material at another point. Then read the reading of the magnetic field measuring instrument and rotate the magnetic field cargo 360 degrees to find the high magnetic field strength value. If it is less than 0.159A/m (0.002Gaus), it can be considered as ordinary goods. On the contrary, the distance between the two points can be increased to 4.6m and the above method can be measured again. If the measurement result is less than 0.418A/m (0.00525gas), it can be considered as dangerous goods transportation. On the contrary, rectification is necessary to meet the requirements. Method 2: Using a magnetic compass, first locate two points on the east/west straight line m in an area without any magnetic field other than the Earth's magnetic field, so that the magnetic compass is at one point, and then place the measured magnetic material at another point. Then read the reading of the magnetic field measuring instrument and rotate the magnetic field cargo 360 degrees to find the high magnetic field strength value. If it is less than 0.5 degrees, it can be considered as ordinary goods. On the contrary, the distance between the two points can be increased to 4.6m and the above method can be used for measurement again. If the measurement result is less than 2 degrees, it can be considered as dangerous goods transportation. On the contrary, rectification is necessary to meet the requirements