  The origin and nature of ultrahigh-energy cosmic rays (UHECRs) are one of the
most intriguing mysteries in particle astrophysics and astronomy. The two
largest observatories, the Pierre Auger Observatory and the Telescope Array
Experiment, are steadily observing UHECRs in both hemispheres in order to
better understand their origin and associated acceleration mechanisms at the
highest energies. We highlight their latest results including on-going
upgrades, AugerPrime and TAx4, and then address the requirements for a
next-generation observatory. We share recent updates and perspectives for a
future ground array of fluorescence detectors, addressing the requirements for
a large-area, low-cost detector suitable for measuring the properties of the
highest energy cosmic rays with an unprecedented aperture.
