frequent flier → τακτικός επιβάτης, τακτικός πελάτης, συνήθης ύποπτος, ενοχλητικός, συχνός ασθενής, υποχόνδριος ασθενής

[spiros]

frequent flyer
frequent flier → τακτικός επιβάτης, τακτικός πελάτης

A person who flies frequently on commercial airliners.
As he flew home every weekend, he considered himself a frequent-flier.
Someone who is habitually a nuisance.
Drunks tend to be the most common frequent fliers.
(medicine, slang, derogatory) A patient who frequents a health facility, with minor or malingering-type presentations.
frequent flyer - Wiktionary