4 means that under standard conditions, the usable length of the runway is greater than or equal to 1800 meters

F The runway represents the wingspan of the aircraft allowed to take off and land and the distance between the outer wheels of the main landing gear (this point It is generally difficult for outsiders to understand, so I won’t go into details. If you want to know, you can ask)

4F is the runway and the highest level of the flight area. The supporting facilities in the 4F level flight area must be able to accommodate the take-off and landing of the Airbus A380 with a full weight (approximately 560t).

If you don’t understand anything, please feel free to ask. I hope it can be helpful to you.