I wouldn't part with mine unless at gunpoint. There is no earthly reason for an airline to retain a passport, other than as a means of keeping you in a country.
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May be that is the whole idea - Before you go off on that dream vacation, how about letting us , the management,know so that we can do a simple thing like trying to put some one else in your place - after all - we have a small toy called an airplane to fly!!!
Not entirely joking - one airline here in this part of the world (not AD) had to cut down on its schedules by 10% virtually overnight - because some of their senior commanders ( but not expats) decided to go where the grass was greener - or I heard browner!
Labour laws are not water tight everywhere Monsieur RD! And sometimes it works against the bean counters too!
Cheerio