The visibility of flights on our map will vary based on several factors, including our coverage in the area and the type of aircraft and transponder on board. Furthermore, for security reasons, some military and government aircraft are blocked and will not show up.
The coverage around the area may not be sufficient to cover all flights landing and taking off. For example, if the aircraft you see doesn't have an ADS-B transponder on board, we will need several receivers from our network in the area to be able to show the aircraft on our maps. This is especially true at low altitudes. Even if the aircraft has an ADS-B transponder (most commercial airlines do) we would still require optimal coverage in the particular area, especially if it is close to the airport. Often the aircraft will only show on our map at higher altitudes, as it becomes easier for their signal to be picked up by our receivers.