What is the test for establishing an easement to allow access to an area of land where there is a long-term use of the land?

Although title to land is to be respected, it is not without limitation. Easements of necessity have long been recognized . (Reese v. Borghi, 216 Cal.App.2d 324, 30 Cal.Rptr. 868.) There is no such an easement here, but one which equity may fairly create. Facility of transportation enhances [10 Cal.App.3d 47] the productivity and worth of lands and of the fruits of the earth. In modern living, rigidity of ownership of every vestige of land must yield somewhat to the welfare of neighbors and of the public. Long since has the concept of ownership to the sky which was a common law notion ('cujus est solum ejus usque ad coelum') given way to the demands of the airplane. So, in lesser manner, it is proper to give a fair, though prudent employment of the equitable doctrine even in favor of a plaintiff and even though his mistaken and harmless encroachment be of recent origin.