Echolocation is not universal among bats. Nearly all species in the suborder Yangochiroptera and the rhinolophoid families produce ultrasonic calls in the larynx and read the returning echoes. Old World fruit bats of the family Pteropodidae, which includes every flying fox, do not.
Instead Pteropus relies on large, forward-facing eyes with a retina rich in rods, plus a strong sense of smell for locating ripe fruit and flowering trees. The genus is one of the few mammal groups in which vision, rather than hearing or olfaction alone, dominates navigation at night. A separate lineage within the family, the genus Rousettus, evolved a crude form of echolocation using tongue clicks rather than laryngeal calls, showing the capacity arose more than once.
Two things are commonly got wrong. Flying foxes are not blind, and the phrase blind as a bat has no basis in any species. Nor is their wingspan a guide to weight: a bat with a 1.4-metre span may weigh about a kilogram.